Together Against Sizewell C Limited, R (on the application of) v Secretary of State for Energy Security and Net Zero

The question at the heart of this appeal is whether the Secretary of State for Business, Energy and Industrial Strategy erred in law by failing to carry out an “appropriate assessment” of the effects on European sites of the permanent supply of potable water to a proposed nuclear power station, either as part of the same project or cumulatively as a separate but connected project, under regulation 63 of the Conservation of Habitats and Species Regulations 2017 (S.I. 2017 No.1012) (“the Habitats Regulations”).

The appeal is against the order of Holgate J. dated 22 June 2023 refusing an application by the appellant, Together Against Sizewell C Limited (“TASC”), for permission to apply for judicial review of the Sizewell C (Nuclear Generating Station) Order 2022 (“the Order”) for the construction, operation, maintenance and decommissioning of a third nuclear power station at Sizewell on the Suffolk coast, known as “Sizewell C”. TASC is a special purpose company, created by members of the local community to oppose the development of the power station.

The Order was made by the Secretary of State for Business, Energy and Industrial Strategy under section 114 of the Planning Act 2008 (“the 2008 Act”) on 20 July 2022. The relevant statutory functions have since been transferred to the Secretary of State for Energy Security and Net Zero, who has therefore been the defendant in these proceedings and is now the first respondent in the appeal. We shall refer to both ministers simply as “the Secretary of State”. The second respondent, Sizewell C Limited (“Sizewell C Ltd.”), formerly NNB Generation Company (SZC) Limited, is the intending developer.

TASC issued the claim for judicial review of the Order on 30 August 2022. The matter first came before Kerr J. on the papers. He concluded that none of the grounds was arguable with a real prospect of success, and refused permission to proceed on 18 October 2022. TASC renewed its application, which became the subject of a “rolled-up” oral hearing before Holgate J. on 22 and 23 March 2023. On 22 June 2023, having reached the same conclusions as Kerr J., for reasons set out in a detailed reserved judgment, Holgate J. made an order refusing permission to proceed with the claim for judicial review on all seven of the grounds that were then pursued.

TASC sought permission to appeal against the order of Holgate J. on five of those grounds. By an order dated 8 September 2023, Coulson L.J. granted permission on two of them, which correspond with grounds 1 and 2 of the claim for judicial review. Both grounds concern the “appropriate assessment” of the means by which a permanent supply of potable water to the proposed power station will be provided. As the question of permission was inextricably linked to the substantive merits, Coulson L.J. directed that the proceedings in this court would be a “rolled-up” hearing, which would in effect consider whether the judge was wrong to refuse permission to apply for judicial review and, if so, immediately consider detailed submissions on the judicial review claim itself – the claim being retained in the Court of Appeal rather than remitted to the High Court for hearing. At the hearing of the appeal, we allowed all parties to make their full detailed submissions on both permission to apply for judicial review and the substantive claim.

Both the Secretary of State and Sizewell C Ltd. contend that Holgate J. was right to hold that neither of the grounds of appeal is properly arguable. They have also filed respondent’s notices under CPR r.52.13(2)(b), inviting the court to uphold the order of Holgate J. for additional reasons.

The appeal raises two main issues:

For the reasons set out in this judgment, we agree with Holgate J.’s conclusions on both issues.

Regulation 63(1) of the Habitats Regulations provides:

Regulation 63(5) states:

Regulation 64(1) provides:

The “competent authority” in this case is the Secretary of State. It is common ground that a “national policy statement” designated under the 2008 Actis a “plan”, and that a “nationally significant infrastructure project” for which development consent is applied for, also under the 2008 Act, is a “project” for the purposes of regulation 63(1) of the Habitats Regulations. What is in dispute in the present case is the ambit of the “project” that had to be assessed under those Regulations. There is no definition of the term “project” in the Habitats Regulations.

It is also common ground that the Sizewell C development is “likely to have a significant effect” on European sites, and therefore that an “appropriate assessment” was required to be carried out under regulation 63(1). An adverse effect on the integrity of two sites – the Minsmere-Walberswick SPA and the Minsmere-Walberswick Ramsar Site – could not be ruled out, in view of the possible impacts on the habitat of the Marsh Harrier (Circus aeruginosus), a species of marshland bird, by noise and visual disturbance from the construction of the proposed development.

Section 103 of the 2008 Act establishes the role of the Secretary of State to decide an application for an order granting development consent for a “nationally significant infrastructure project”. The proposed Sizewell C development is a nationally significant infrastructure project for these purposes.

The relevant statutory framework for obtaining developmentconsent for nationally significant infrastructure projects was described by Lord Hodge and Lord Sales in R. (on the application ofFriends of the Earth Ltd.) v Secretary of State for Transport [2020] UKSC 52, [2021] PTSR 190, at paragraphs 19 to 38. It includes those provisions which govern the designation of a national policy statement under section 5 of the 2008 Act, following a process of consultation and an appraisal of sustainability and strategic environmental assessment (“SEA”) under the Environmental Assessment of Plans and Programmes Regulations 2004 (SI/2004/1633).

Under section 104, the Secretary of State must have regard to any relevant national policy statement designated under section 5(1) (section 104(2)), and must decide the application in accordance with it, subject to specified exceptions (section 104(3)). Under section 106(1)(b), he may disregard representations relating to the merits of policy set out in a national policy statement.

There are two relevant national policy statements in this case: EN-1, which is the Overarching National Policy Statement for Energy (“EN-1”), and EN-6, which is the National Policy Statement for Nuclear Power Generation (“EN-6”). Both were “designated” in July 2011. EN-1 sets out the approach to deciding applications for development consent (in paragraphs 3.1.1 to 3.1.4). Paragraph 3.5.1 of EN-1 acknowledges that there is “an urgent need for new electricity generation plant, including new nuclear power” to enable the United Kingdom to meet its energy and climate change objectives. EN-6 identifies the site at Sizewell, and seven other sites, as potentially suitable for a new nuclear power station.

Section 114 of the 2008 Act provides that the Secretary of State must either make an order granting development consent, or refuse development consent. Under section 61, he must decide whether a “Panel” (referred to in this judgment as “the examining authority”) or a single person will be appointed by him to “handle” the application. Where a Panel has been appointed, section 74 requires it to undertake an examination of the application and produce a report to the Secretary of State on its findings and recommendations.

Section 37(1) of the Water Industry Act 1991 imposes a general duty on a water undertaker to develop and maintain an efficient and economical system of water supply within its area. There is a concomitant duty to ensure that the necessary arrangements have been made for providing supplies of water to premises in that area and to persons who demand them, and to carry out all necessary maintenance, improvements and extensions to the water undertaker’s water mains and other pipes to enable it to fulfil its statutory duties.

Under section 37A, a water undertaker is required to plan to meet the demand for water within its area by means of a water resources management plan. Section 37A(6)(c) establishes that water undertakers must publish water resources management plans “not later than the end of the period of five years beginning with the date when the plan … was last published”.

Section 55 requires the water undertaker to take steps to provide a water supply when requested to do so by the owner or occupier of premises in the area for non-domestic purposes, subject to certain conditions. The terms and conditions of such supply are to be determined by agreement between the parties, or in default by OFWAT, according to what appears to be reasonable (section 56). Section 55(3)(b) contains a proviso that the water undertaker shall not be required to take steps to provide a new supply to any premises under section 55 if this would put at risk its ability to meet any of its existing or probable future obligations to supply water for domestic or other purposes.

It is not in dispute that a water resources management plan is a “plan” for the purposes of regulation 63(1) of the Habitats Regulations. Any such plan is subject to its own independent environmental assessments, including under the Habitats Regulations.

The “water undertaker” for the purposes of sections 37A and 55 of the Water Industry Act 1991 is Northumbrian Water Limited (“NWL”). Under section 37A, NWL is preparing its Water Resources Management Plan 2024 (“WRMP24”) to set its strategy for meeting water demand for Essex and Suffolk in the period from 2025 to 2050.

Sizewell C Ltd. made its application for a development consent order on 27 May 2020. It was unable at that time to identify a permanent supply of potable water for the proposed power station, but maintained that this would become clear when a water resources management plan had been prepared by NWL. It was envisaged that NWL would supply the potable water through its local subsidiary, Essex & Suffolk Water.

An examination was held between 14 April and 14 October 2021. In July 2021 Sizewell C Ltd. provided an initial “Water Supply Strategy Report” in which itstated that the supply of potable water for the construction and operation of Sizewell C would come from NWL’s existing supply headroom. However, NWL told the examining authority that they would not be able to meet the demand from that headroom, and that additional infrastructure would likely take until September 2026 (at the earliest) to deliver. In response, Sizewell C Ltd. proposed the construction of a temporary desalination plant to supply potable water during the early construction phase.

Water supply was discussed at the examining authority’s “Issue Specific Hearing 11” on 14 September 2021. NWL explained that the required review of its ongoing modelling work to understand whether there was a sustainable source of water supply was unlikely to be complete by the close of the examination. Natural England (“NE”) said that it was unable to advise whether adverse effects on designated sites could be ruled out as a result of the necessary water infrastructure. In response to a question by the examining authority, the Office forNuclear Regulation stated that Sizewell C could not fulfil its Licence Conditions, and thus could not begin operation, without a permanent potable water supply.

On 25 February 2022 the examining authority submitted its “Report on Findings and Conclusions and Recommendation” to the Secretary of State. The report stated (in paragraphs 5.11.286 and 5.11.287):

In its conclusions on water supply it observed that that “there was still no certainty as to where the permanent water supply would be sourced from and how the necessary water would be transferred to the Proposed Development” (paragraph 5.11.290). It stated (in paragraph 5.11.292):

It therefore suggested that the Secretary of State might consult Sizewell C Ltd., NWL, the Environment Agency and other interested parties “to identify whether there has been progress on the identification and assessment of effects of a sustainable permanent water supply for the Proposed Development, prior to making a decision on the application for the DCO” (paragraph 5.11.296).

In its conclusions on the planning balance and the case for development consent, the examining authority said (in paragraphs 7.5.7 and 7.5.8):

On the “Habitats Regulations Assessment”, under the heading “Likely Significant Effects”, it said this (in paragraph 7.6.3):

In section 10 of its report, where it summarised its findings and conclusions, the examining authority said (in paragraph 10.2.19):

It recommended (in paragraph 10.3.1) that “unless the outstanding water supply strategy can be resolved and sufficient information provided to enable the Secretary of State carry out his obligations under the Habitats Regulations, the case for an Order granting development consent for the application is not made out”.

In a letter dated 18 March 2022 the Secretary of State requested further information from Sizewell C Ltd., the Environment Agency, NE and the Office for Nuclear Regulation. Referring to a letter from NWL’s solicitor dated 23 February 2022, which said that NWL was unable to meet the required demand for water supply from existing resources, he asked Sizewell C Ltd. to explain what progress was being made to securing a permanent water supply. He said (in paragraphs 3.3 and 3.4 of his letter):

In its letter in response, dated 8 April 2022, Sizewell C Ltd. relied on NWL’s duty under the Water Industry Act 1991 to identify, through WRMP24, new water resources to meet the forecast demand for its region, including the proposed power station. It said that “the Secretary of State can be reassured … that good progress is being made to identify alternative supplies that are sustainable through NWL’s [WRMP24] process” (paragraph 2.1.2). It continued (in paragraph 2.1.8):

Work on the draft of WRMP24 was “well advanced”. WRMP24 would “be subject to a fully integrated environmental appraisal, including Strategic Environmental Assessment (SEA) and where necessary, Habitats Regulations Assessment”(paragraph 2.1.9). And “options for supplementing the region’s water supply [were] being actively considered as part of the [WRMP24] process” (paragraph 2.1.10). It was “for that process to identify and determine the environmental acceptability of those options and the Secretary of State may make a decision on the DCO confident that the duty will be effectively satisfied” (paragraph 2.1.11).

Sizewell C Ltd. concluded (in paragraphs 2.1.15 and 2.1.16):

In answer to the question about the possibility of using the proposed desalination plant to provide a permanent potable water supply, Sizewell C Ltd. said (in paragraphs 2.1.20, 2.2.1 and 2.2.3):

On 25 April 2022 the Secretary of State invited comments from interested parties on those responses. In its letter in reply dated 23 May 2022, TASC raised objections to a permanent desalination plant but offered no comments on the prospect of WRMP24 identifying a means of supplying water to the power station. It maintained its position that the lack of a guaranteed permanent water supply meant that not all significant environmental effects were being assessed at the development consent stage.

In his decision letter, dated 20 July 2022, the Secretary of State set out his conclusions on this topic and the reasons for them under the heading “The Secretary of State’s Consideration of Water Supply”. Addressing the specific question of long-term water supply to the power station he stated (in paragraph 4.44):

He went on to say (in paragraph 4.49):

The Secretary of State expressly disagreed with the examining authority’s view that even if the water supply was considered to be a separate project the cumulative effects associated with it should be assessed before development consent was granted for the nuclear power station. On this question he said (in paragraph 4.50):

The Secretary of State noted (in paragraph 4.51) that Sizewell C Ltd.’s “original and preferred water supply connection was a direct link from Barsham” and that information had been supplied about the cumulative effects of this option. He continued (in paragraph 4.52):

He reached the following further conclusions (in paragraphs 4.55 to 4.60):

While acknowledging that a permanent desalination plant was not Sizewell C Ltd.’s preferred means of supplying water to the power station, the Secretary of State also dealt with the concerns raised about this option (in paragraphs 4.61 and 4.62):

Amplifying what he had already said on the means of supplying water to the power station, he then said:

Turning to the Habitats Regulations, the Secretary of State said (in paragraphs 4.65 and 4.66):

In his “Overall Conclusion on Water Supply” he said (in paragraphs 4.67 to 4.69):

Having satisfied himself that there was no impediment to his doing so, and in disagreement with the examining authority’s recommendation, the Secretary of State concluded that development consent for the power station should be granted, and he duly made the Order (paragraph 7.15, under the heading “The Secretary of State’s Consideration of the Planning Balance”).

Holgate J. set out the factual and legal background and summarised the grounds of challenge to the Order before addressing each of those grounds in turn. On the first ground of the claim, he said (at paragraph 70) that “[the] question of what is the project in any particular case is a matter of judgment for the decision-maker, here the Secretary of State”, and “[that] judgment may only be challenged in this court on Wednesbury principles”. He cited a number of authorities for that proposition, including Bowen-West v Secretary of State for Communities and Local Government (2012) Env. L.R. 22 and the recent decision of this court in R. (on the application of Ashchurch Parish Council) v Tewksbury Borough Council [2023] PTSR 1377.The issue in this case was “whether [the Secretary of State] took into account any consideration which was legally irrelevant and, if not, whether his judgment was otherwise irrational”.

The judge first considered (at paragraph 72) the acknowledgment in R. (on the application of Larkfleet Limited) v South Kesteven District Council [2016] Env. L.R. 4, that the mere fact of two sets of proposed works having a cumulative effect on the environment did not make them a single project, although their cumulative effects might still need to be assessed. In that case the court had also warned that a local planning authority should be “astute to ensure that a developer has not sliced up what is in reality one project in order to try to make it easier to obtain planning permission for the first part of the project and thereby get a foot in the door in relation to the remainder” – a process referred to as “salami-slicing”. However, Holgate J. concluded (at paragraph 77) that this was not such a case.

Holgate J. referred (in paragraph 73 of his judgment)to the list of factors adumbrated by Lang J. in her second judgment in R. (on the application of Wingfield) v Canterbury County Council [2019] EWHC 1975 (Admin) (at paragraph 64) which may be taken into account in determining the extent of a “project”. He noted that Lang J. had made it clear that those factors were not exhaustive, and that the weight to be given to them will depend on the circumstances of each case and is a matter for the decision maker. He pointed out (at paragraph 74) that one of those factors, “functional interdependence”, would normally mean that each part of the development is dependent on the other.

He referred (at paragraph 77) to the fact that it had been initially assumed or believed that NWL would meet its obligations under the Water Industry Act 1991 by providing a permanent water supply at Barsham and a transfer main to Saxmundham. The provision of that infrastructure by NWL was thereforenot included in Sizewell C Ltd.’s application for development consent. It was only later that the present uncertainty emerged about the form that the long term supply of potable water would take. Sizewell C Ltd. was not “keeping its options open” by refusing to commit to a permanent desalination plant. It had “made it plain that it wishes to rely upon the solution that NWL says it will be able to deliver through the WRMP24 process and not upon permanent desalination on-site”. But the Secretary of State’s decision “[recognised] that in the unlikely event of NWL being unable to provide a solution, [Sizewell C Ltd.] would seek to provide a desalination plant (DL 4.66)” .

Holgate J. rejected TASC’s argument that the Secretary of State had taken into account immaterial considerations, which he summarised (at paragraph 78) – an argument it had sought to base on the judgment of Andrews L.J. in Ashchurch. In this case, unlike Ashchurch, the Secretary of State had expressly considered whether a particular matter (here, the provision of a permanent water supply) formed an integral part of the Sizewell C development and had concluded it did not (paragraph 86). He was entitled to take into account the fact that the permanent water supply was not part of the application for development consent and “would be dealt with under a subsequent, separate process and … subject to an integrated environmental assessment”. There was “no basis upon which [his] evaluative judgment can be said to be irrational” (paragraph 90).

In the judge’s view TASC’s argument had much wider implications. Its consequence “would be that where a new supply has yet to be identified by the relevant utility company, decisions on those development projects would have to be delayed until the company is able to define and decide upon a proposal”. That approach “would lead to sclerosis in the planning system which it is the objective of the legislation and case law to avoid” (paragraph 91).

As for the complaint that a permanent desalination plant was not treated as part of the Sizewell C project, Holgate J. said there was “no obligation to assess a hypothetical scheme (Preston New Road Action Group v Secretary of State for Communities and Local Government [2018] Env. L.R. 18] at [75])”. Sizewell C Ltd. considered a permanent desalination plant was unlikely to be necessary and was “not currently proposing that option”. The Secretary of State’s conclusion that such a plant was not an integral part of the Sizewell C project “cannot be faulted” (paragraph 92).

On the second ground, Holgate J. said it was “well-established that a decision-maker may rationally reach the conclusion that the consideration of cumulative impacts from a subsequent development which is inchoate may be deferred to a later consent stage” (paragraph 97). There was no merit in the argument that deferring the consideration of cumulative impacts to a subsequent consent stage would cause the application of the IROPI test to be “distorted, biased or watered down in some way” (paragraph 102). Here the “cumulative impact [would] have to be assessed properly in accordance with the legislation without any bias or distortion”. The “benefits” of the power station “could not be taken into account in a future IROPI assessment without also taking into account the disbenefits” (paragraph 103). A “section 55 agreement” was expected to be signed in early 2024, after the WRMP24 process, in which “the integrated environment assessment will have been carried out” (paragraph 104).

Mr David Wolfe K.C., for TASC, accepted in the course of argument that we are not concerned here with a case of “salami-slicing” in the proper sense of that expression in this legal context. In its true sense in the context of environmental impact assessment and Habitats Regulations assessment, the concept of “salami-slicing”, or “project-splitting”, involves the deliberate dividing of a single project into individual parts in an attempt to avoid the need for environmental impact assessment of the whole (see the leading judgment in Preston New Road Action Group, at paragraph 69, and the judgment of Lang J. in Wingfield, at paragraphs 51 and 71).

As is clear in the relevant European and domestic case law, and as Holgate J. acknowledged, a distinction must be drawn between, on the one hand, cases where “salami-slicing” or “project-splitting” has been attempted and an assessment avoided, and, on the other, cases such as this where an assessment has been carried out but the legal adequacy of that assessment itself is called into question (see the judgment of Laws L.J. in Bowen-West, at paragraph 32).

A further principle, also well established, is that two connected projects may proceed separately, and their cumulative effects be assessed, whether under the EIA Regulations or under the Habitats Regulations, either in two stages or at the second, but as soon as those cumulative effects can be identified for meaningful assessment (see the judgment of Sales L.J., as he then was, in Larkfleet, at paragraphs 36 to 38, and also his judgment in R. (on the application ofForest of Dean (Friends of the Earth)) v Forest of Dean District Council, [2015] PTSR 1460 at paragraphs 13 to 19). A “staged approach” to assessment is, in principle, legitimate and will prevent what has been described as “sclerosis in the planning system” (see the judgment of Sales L.J. in Forest of Dean District Council, at paragraph 18).

In some cases this will be the obvious and only realistic course to take. It can enable the first project to receive the permission or consent it requires, without preventing or prejudicing a proper assessment of likely cumulative effects. If done correctly, it can ensure that a cumulative assessment of the two projects is undertaken in accordance with the legislative requirements, any suitable mitigation proposed, and a decision taken either to refuse or permit the second project to proceed. It can overcome the risk of an incomplete and unreliable cumulative assessment being produced at the first stage, when the first project is being considered and the second is still uncertain in its form and timing (see the judgment of Holgate J. in Pearce v Secretary of State for BEIS [2021] EWHC 326, at paragraph 117). It can prevent unnecessary delay for decision-makers, developers and third parties. And it can be adopted without compromising the “precautionary approach” (see the opinion of Advocate General Kokott in Commission v United Kingdom (Case - 6/04) [2005] ECR I-9017).

None of this undermines the principle expressed by the Court of Justice of the European Union in its judgment in Inter-Environnement Wallonie ASBL v Conseil des Ministres (C-411/17) [2020] Env. L.R. 9 (at paragraph 143), that an “appropriate assessment” for the purposes of article 6(3) of the Habitats Directive mustbe carried out before the relevant authority permits the plan or project to go ahead, even though there are several further steps in the consent procedure. As the court in that case emphasised, this assessment “should, in principle, be carried out as soon as the effects which the project in question is likely to have on a protected site are sufficiently identifiable”. But the corollary of this, as both respondentssubmitted, is that where the cumulative effects in question are not yet capable of being sufficiently identified for proper assessment at the consenting stage for the first project because the second is still unidentified, the assessment of cumulative effects can lawfully await the consenting stage for that second project.

Mr Wolfe’s main argument on this issue was essentially that the Secretary of State ought to have regarded the water supply, whether in the form of a permanent desalination plant or some other measures yet to be decided upon by NWL, as composing an indivisible part of the same project. The Secretary of State’s failure to recognise this, and to insist on an assessment of the whole project, was an error of law. Holgate J. was wrong to conclude that there is no principle under the habitats legislation compelling a decision-maker to undertake assessment at the “earliest possible stage”. The permanent supply of water was “functionally interdependent” with the power station, which could not be licensed to operate without it. Holgate J. had confused Sizewell C Ltd.’s need for a permanent supply of water to the power station with the statutory obligation of NWL to provide a supply of water to the area for which it was responsible as water undertaker. In doing so, he had disregarded the additional infrastructure and, possibly, abstraction that would not have been required in the absence of the power station, and the effects that it would have on European sites.

Prominent inMr Wolfe’s argument was his submission that, both at the time of the examination and when the Secretary of State made his decision, it was possible to identify a permanent supply of potable water to the power station, in the form of a permanent desalination plant. This could have been built on land within Sizewell C Ltd.’s control. The Secretary of State’s reliance on “separate ownership”, in paragraph 4.49 of the decision letter, was misplaced. The fact that a permanent desalination plant was not included in the application for a development consent order was also immaterial, as was the fact that this was not Sizewell C Ltd.’s preferred option. It could not be right, as a matter of law, that a developer is able to gain development consent on the basis of an inadequate assessment under regulation 63 of the Habitats Regulations simply by declining to commit itself to implementing a particular proposal as part of its project.

Mr Wolfe also argued that Holgate J. should not have been concerned by the “wider implications” of TASC’s challenge, and the risk of “sclerosis in the planning system”. TASC’s challenge went only to the unlawful failure to assess, under the Habitats Regulations, the effects on European sites of the water supply necessary for the operation of the proposed power station, and no wider than that.

Opposing that argument, Mr James Strachan K.C., for the Secretary of State, and Mr Hereward Phillpot K.C., for Sizewell C Ltd., submitted that on application of the appropriate Wednesbury principles it was reasonably open to the Secretary of State to conclude that the means by which NWL would eventually perform its own statutory obligations, under the Water Industry Act 1991, to provide a permanent supply of potable water to the power station by 2035 was not part of Sizewell C Ltd.’s project. Even if – as Mr Wolfe had contemplated in his written argument – the identity of the project was ultimately a matter of fact for the court to decide for itself, the same answer emerges, because it was beyond doubt that the means by which potable water is supplied to the site was not part of the project the Secretary of State was considering. It was not included in the application for a development consent order. And it would not be possible to identify and assess it until NWL had formulated and promoted its own proposals under the Water Industry Act 1991, which would, anyway, engage the Habitats Regulations.

No definition of a “project” is to be found either in the Habitats Directive or in the Habitats Regulations. It is agreed however, and we accept, that there is no material difference in the meaning of this concept between the legislation for environmental impact assessment and that for the assessment of the effects on European sites, and that case law concerning the former illuminates the latter (see the judgment of the CJEU in Inter-Environnement Wallonie, at paragraphs 122 to 124).

Nor, as we understand it, was there ultimatelyany real dispute about the correct approach for the court to adopt when it has to consider whether a decision-maker has fallen into error either in determining the nature and scope of a particular project or ascertaining whether two or more developments are properly to be regarded as forming a single project. As Mr Strachan and Mr Phillpot submitted, relevant case law is consistent and clear on the principle that these questions are not matters of law for the court but of fact and evaluative judgment for the decision-maker itself, subject to review by the court on a conventional Wednesbury basis (see the judgment of Andrews L.J. in Ashchurch, at paragraphs 81, 83, 100 or 105, the judgment of Sales L.J. in Smyth v Secretary of State for Communities and Local Government [2015] EWCA Civ 174; [2015] PTSR 1417, at paragraph 80, and the judgment of Laws L.J. in Bowen-West, at paragraphs 39 to 42, echoed in decisions of the Planning Court; see, for example, the judgment of Lang J. in Wingfield, at paragraph 63).

A parallel principle applies, with the endorsement of the Supreme Court, to the exercise by the decision-maker of its discretion on the information to be included in an environmental report under article 5(2) and (3) of the SEA Directive (see the judgment of Lord Hodge and Lord Sales in Friends of the Earth at paragraphs 142 to 148, approving the reasoning of Sullivan J., as he then was, on the approach to challenges asserting inadequacy in an environmental statement under the EIA Directive, in R. (on the application of Blewett) v Derbyshire County Council [2004] Env. L.R. 29, at paragraphs 32 to 41).

What constitutes the relevant project, as a matter of fact and the decision-maker’s evaluative – or planning – judgment, will always depend on the facts and circumstances of the particular case. And it is not possible to state any hard and fast rules governing a decision-maker’s exercise of judgment. That exercise of judgment carries a wide range of discretion. There are, however, three general points to be made about it.

First, as we have said, the decision-maker must be alert to the mischief of “salami-slicing”, or “project-splitting” being resorted to in an attempt to evade the requisite assessment. Secondly however, in a case where two or more separate developments with some physical or functional connection to each other are being promoted through different or successive processes, the likelihood or even certainty of their having cumulative effects on the environment, or on a specific habitat, does not mean that they necessarily compose a single project. The effects may be cumulative, but the projects themselves separate and different. And thirdly, without seeking to prescribe the method by which a decision-maker should judge the nature and scope of a project, or the existence or absence of a single project rather than two or more, it is possible to identify several factors capable of influencing such an exercise. As Lang J. suggested in Wingfield (at paragraphs 64 and 73 of her judgment), without contradiction by this court in Ashchurch (see the judgment of Andrews L.J., at paragraph 81), the relevant considerations can include “common ownership”, “functional interdependence”, the question of whether the project stands on its own and would be promoted independently of other development, and the question of “simultaneous determination”. As Holgate J. rightly acknowledged, whether one or more of these potentially relevant factors is especially significant, and the weight it should be given, are for the decision-maker to assess, on the facts of the case in hand.

In Ashchurch theoutcome turned very much on the peculiar facts. The bridge in question had been dealt with separately from the housing development it was intended to serve, andthe local planning authorityhad failed to confront the question of whether this was a single project (see the judgment of Andrews L.J., at paragraph 96). In this case, however, as Holgate J. recognised (in paragraphs 79 to 87 of his judgment), the circumstances are quite different. We are not concerned here with proposed infrastructure integral to a development of housing, but with a water undertaker’s future provision of water to a power station in performing its own statutory duty to do so. The means by which this would be done were still uncertain when the decision on development consent was made, and would remain so for some time. A meaningful assessment of its effects could not yet be made.

With the three general points we have mentioned in mind, and in agreement with Holgate J., we cannot fault the Secretary of State’s exercise of his own judgment on the nature and scope of the project before him and its relationship to the future project for the supply of potable water to the power station. His findings and conclusions on this question were lawful. His exercise of judgment upon it was not irrational. He did not take into account immaterial considerations. Nor did he err in law in any other way.

No criticism can be made of the Secretary of State’s conclusion that the proposed development of the power station itself and the relevant parts of WRMP24, once published, were different projects, which did not have to be dealt with together in a single “appropriate assessment” complying with regulation 63 of the Habitats Regulations. The Secretary of State’s conclusions in paragraphs 4.49, 4.65 and 4.66 of his decision letter, are legally impeccable. There is no force in the contention that he was wrong to conclude as he did. That contention demonstrates a disagreement with the Secretary of State’s exercise of judgment, as decision-maker, on the facts before him. It does not demonstrate, however, that he erred in law in that exercise of judgment. Nor does it indicate irrationality or any other unlawfulness in his conclusions. On this we agree with the judge. He was satisfied that, in the circumstances of this case, the ultimate means, or “source”, of the permanent supply of potable water to the power station was not part of the project that was properly under consideration at this stage, and for which an “appropriate assessment” was required under the Habitats Regulations.

Like the judge, we think the factors that obviously weighed with the Secretary of State in ascertaining the nature and scope of that project were all lawfully taken into account by him. They correspond to the approach suggested by Lang J. in Wingfield (at paragraph 64), which we think was essentially sound. On the facts here they seem valid and persuasive considerations, clearly bearing on the identity of the project. They reflect good sense. When taken together they are, we think, compelling.

It was plainly a relevant factor that no particular system of permanent water supply, whether provided by NWL as water undertaker, or in the form of a desalination plant, or some other infrastructure, had been actively proposed or committed to in the application for a development consent order. There was no legal compulsion on Sizewell C Ltd. to promote in its application any particular form of water supply. Its project was not deficient for the lack of such a proposal, or incapable of being the subject of a lawful “appropriate assessment” under the Habitats Regulations. The Secretary of State’s conclusions in paragraph 4.59 of the decision letter do not betray any legal error.

It was also relevant that the site of the proposed power station did not extend to the land that would or might be affected by the provision of water infrastructure. The land and land ownership were separate. The Secretary of State was entitled, and in our view right, to take this consideration into account, as he did in paragraph 4.49. His reference to “separate ownership” in this context was apt. If it was meant to convey the idea of separate responsibilities, which isnot what the Secretary of State actually said, that would not have been incorrect.

As for “functional interdependence”, though the Secretary of State did notuse that expression, he rightly recognised, in the same paragraph, that the proposed development of the power station and the WRMP24 process for the “sourcing of water” as “separate projects” were “subject to distinct and asynchronous determination processes”. He emphasised that “these projects are stand-alone, given that NWL has a duty to undertake its WRMP24 regardless of whether or not the Proposed Development proceeds”. The fact that the development consent process for the power station under the 2008 Act was, both statutorily and in its timescale, a different process from the preparation by NWL of a water resources management plan under the Water Industry Act 1991 was clearly relevant, and significant. But this is not merely to say that the two procedures were under different legislative regimes. It is also to recognise that the provision of a supply of water to the power station was only one part of a much broader undertaking by NWL to provide water to meet demand in the area of Essex and Suffolk for which it had statutory responsibility. That broader undertaking required it to perform various functions under the Water Industry Act 1991, including the specific obligation to prepare a water resources management plan. The carrying out of those statutory functions was obligatory for it as a water undertaker, regardless of whether development consent was granted for the power station. As one sees in paragraph 4.49 of the decision letter, the Secretary of State was conscious of this, and its relevance as a factor that went against the provision of a permanent water supply by NWL being regarded as part of the same project as the power station itself.

The preparation of the water resources management plan by NWL as water undertakerwas going to be subject to assessment under both the Habitats Regulations and the legislative scheme for environmental impact assessment. But this had not yet happened. At the time of the Secretary of State’s decision on the application for a development consent order, it was still not certain what the permanent supply of potable water to the power station in 2035 would be. It remained open to NWL to select its own desired option for supplying water to the power station, which it might later decide to replace with another. And Sizewell C Ltd., from the perspective of the operator of the power station, might have no distinct preference of its own, so long as the chosen option was effective and reliable.

All thiswas clearly in the Secretary of State’s mind when he made his decision. He did not misdirect himself in having regard to the separate statutory processes and the uncertainties surrounding the outcome of the water resources management plan process when he treated the power station and the water supply as separate projects. On the contrary, he was unquestionably right to do so.

There was no inevitable link between the two projects. The power station could be built before a permanent supply of water was in place. It was always understood that its operation was going to require a permanent supply of potable water, which could involve water being supplied either by a utility company – NWL as water undertaker – or by some other means if that turned out to be necessary. This did not mean, however, that the method of water supply ultimately chosen by NWL, whatever it might be, was integral to the project of constructing the power station. It could properly be seen as extrinsic to that project.

Mr Wolfe put great emphasis on the likelihood of a permanent desalination plant being developed and operated by Sizewell C Ltd.. In our view, however, his argument gains no strength from that. Far from being a firm proposal, such development was not proposed at all. Sizewell C Ltd. had misgivings about its limitations, and would only resort to it as a fall-back in default of a mains supply. Its intention was to rely on the water resources management plan process instead. This had been made clear in the exchanges that took place after the examining authority had submitted its report to the Secretary of State. Permanent desalination was not expected to be the means of supplying water to the power station. It was not part of the project. The application for a development consent order did not include it. Development consent was not granted for it. Paragraphs 4.61 to 4.63 of the Secretary of State’s decision letter accurately record the position. His conclusion in paragraph 4.63 that further, more detailed assessment of a permanent desalination plant was unnecessary is both unsurprising and, in our view, perfectly lawful.

We share Holgate J.’s concern that the approach contended for by Mr Wolfe could produce “sclerosis in the planning system”. It would seem to imply that, as a general rule, the infrastructure that might later be used by a utility company to supply water, electricity, gas or sewerage to a majordevelopment would fall to be considered as part of the development itself, with the potential consequence that decision-making on that development would have to await the utility company’s own choice of its preferred means of supply. We do not find persuasive Mr Wolfe’s submission that Sizewell C’s need for a permanent supply of water can be distinguished from the comparable requirements of other development for such services.

Standing back from the submissions made on either side, we can see no justification for an argument that in this case the rigour of “appropriate assessment” under the Habitats Regulations has been unlawfully avoided by the Secretary of State’s treatment of the power station development itself and the arrangements yet to be made for the permanent supply of water to the power station as separate projects. What one sees here is a realistic and legitimate use of the “staged approach” approved by this court in Larkfleet and Forest of Dean District Council and by Advocate General Kokott in Commission v United Kingdom. It should be remembered that in the process of designating EN-1 and EN-6 as national policy statements, which necessarily preceded the development consent process, Sizewell, as a location for the development of a third nuclear power station, had already undergone assessment under the Habitats Regulations. The power station project has itself been subject to an “appropriate assessment” under regulation 63, in which all “sufficiently identifiable” effects were assessed as soon as they realistically could be assessed, among them the effects of a pipeline to Barsham. Whatever means of supplying water to the site is decided upon by NWL in the WRMP24 process will also be subject to the “appropriate assessment” regime, entailing – if necessary – cumulative assessment of the effects on European sites.

For those reasons, we consider that the judge was right to reject Mr Wolfe’s submissions on this issue and there is no reason for us to reach a different conclusion in the light of the submissions made on appeal. The contention that the Secretary of State lapsed into public law error in treating the power station proposed in the application before him as the project with which he was dealing is, in our view, untenable.

The Secretary of State did not mistake the true nature and scope of the project before him. He did not differentiate artificially, or incorrectly, between that project and the separate project that would be embodied in the provision of a permanent supply of potable water to the power station. He was entitled in law, and in our opinion clearly right, to regard them as two separate projects. We agree with the analysis to this effect set out by Holgate J. in his judgment.

Our conclusion here is, we think, consistent with the ample case law bearing on this issue. We acknowledge that in Larkfleet Sales L.J. was prepared to contemplate the court taking upon itself the task of ascertaining what the project was (see paragraphs 45 to 51 of his judgment). But he plainly favoured a conventional Wednesbury approach (see paragraphs 40 to 44). And as we have said, this court has consistently done so since. If, however, we were wrong to approach the matter on that basis, and ought instead to have seen it as a matter of law for the court, we would have had no hesitation in coming to the same conclusion. We would then have held for ourselves that on the facts of this case the project was indeed the power station development alone and did not extend to any proposals for the permanent supply of potable water.

Mr Wolfe’s argument on this ground was put forward in the alternative to his submissions on ground1. The thrust of it was that, even if the water supply was not part of the same project as the power station, the Secretary of State erred in law in failing to conduct a cumulative assessment of the effects of the power station and the water supply on European sites. It was wrong in principle to grant development consent for the power station without first carrying out a cumulative assessment of the effects of that development together with those of the water supply necessary for its operation.

Holgate J. was wrong, submitted Mr Wolfe, to hold that the inchoate nature of a proposal excused cumulative assessment. This was not a case in which the first project was independent of the second and was not going to have harmful effects on a European site, so that any such effects could properly be considered at the later stage. The judge should have accepted that TASC’s “foot in the door” argument was cogent. If a cumulative assessment had been carried out, as it ought to have been, when the development consent order application was being determined, it might have led to a refusal of consent. Although it would be possible to carry out a cumulative assessment when the water supply proposal was being considered, this would only be done after the power station had gained consent. This would create the strongest possible IROPI justification for the proposed water supply. It was unrealistic to think that the requisite approval forthe water supply would then be withheld.

Further, or alternatively, Mr Wolfesubmitted that it would be contrary to the Habitats Regulations to assess the water supply separately and at a later stage. If the water supply was not approved at that later stage, the power station would have been partially or wholly constructed, with the environmental damage that this would entail, but would not be capable of being operated. What was required by the Habitats Regulations was an assessment of the power station together with the desalination plant as a possible water supply.

We reject that argument, for these reasons – which reflect some of our discussion of ground 1.

First, as the judge correctly noted (in paragraph 99 of his judgment), ground 2 is predicated on the fact that the provision of the permanent water supply does not form part of the Sizewell C project. It is a different, and separate, project.

Secondly, as the judge rightly observed (at paragraph 97), it is well established that a decision-maker may rationally reach the conclusion that the consideration of cumulative impacts arising from a subsequent development that is still inchoate may be deferred to a later consent stage (see the judgment of Sales L.J., with which the other members of the court agreed, in Forest of Dean District Council (at paragraphs 10 to 13), and also his judgment in Larkfleet (at paragraphs 37 to 38), again with the agreement of the other members of the court).

Thirdly, the decision of the Secretary of State to defer assessment of the impacts of the provision of a permanent water supply to a later stage was a rational, lawful decision. There was insufficient detailed information on the precise means by which a permanent water supply would be provided. NWL was appraising different options and there was a reasonable level of certainty that it would identify a permanent water supply before the first reactor was commissioned (see paragraph 4.44 of the Secretary of State’s decision letter). However, there was insufficient detailed information available as to where new sources of water would be available and how the water would be conveyed to the power station. The permanent water supply would, once identified, be subject to its own assessment. That, as the judge correctly held (at paragraph 98), was a rational approach.

Fourthly, we do not accept Mr Wolfe’s submission that there would be no proper assessment of the impacts of the permanent water supply at that later stage, and that the necessary approval would inevitably be granted, because, by then, the power station would be under construction. There is no evidential basis for assuming or inferring that the relevant regulators would fail to carry out their statutory duties to assess whether the permanent water supply would adversely affect the integrity of a European site and, if so, whether there were IROPI which justified approval. As the judge observed (at paragraph 102 of his judgment), if the benefits of granting consent for the permanent water supply were said to include the overall benefits of the power station being operational, the harms of the Sizewell C project would also have to be included in the assessment. Any failure by relevant regulators to interpret or apply the Habitats Regulations correctly would, of course, be susceptible of legal challenge.

Fifthly, there is no proper basis for considering that the decision to defer assessment of the permanent water supply was irrational because of the risk that the power station might be partially or wholly constructed but not be capable of operation in the absence of approval for a permanent water supply. On the facts, such a prospect was speculative and theoretical. NWL was aware of its statutory duties to supply water and was in the process of appraising options for ensuring that a permanent water supply was available for the power station. There was a reasonable level of certainty that this would result in a permanent water supply being provided. Failing that, there were other options including the possibility of a permanent desalination plant, which, subject to the requirement for appropriate assessment in regulation 63, could provide a satisfactory solution. That was, in our view, a rational approach on the material before the Secretary of State.

As a matter of law – to repeat what we have said on ground 1 – the Secretary of State was entitled when assessing the impacts of granting consent for Sizewell C to defer assessment of the impact of a separate project, such as the provision of a permanent water supply, if it was not reasonably possible to assess those at that earlier stage. The argument presented for TASC, in effect, amounts to a reversal of the legal position and would a require a decision on the earlier project to be delayed until the details of a different project became available so that both projects could be assessed together. That is not the current law. The observations of Sales L.J. in Larkfleet on the Environmental Impact Assessment Directive apply equally to the Habitats Regulations. The aim is to ensure appropriate scrutiny under the Habitats Regulations to protect European sites whilst avoiding undue delay in the operation of the planning system (see the judgment of Sales L.J. in Forest of Dean District Council, a paragraph 13). Such delay, and a disproportionate interference with the public interest and the rights and interests of landowners and developers, would be likely to occur if the position were that the impacts of every related project had to be definitively assessed before any of them could be allowed to proceed.

Finally, as we have concluded on ground 1, the Habitats Regulations did not require an appropriate assessment of a permanent desalination plant as a potential permanent water supply before development consent was granted for the power station. The desalination plant was not part of the project. It was unlikely to form a project in its own right at a later stage. It was purely a “fall-back” option for meeting the unexpected scenario that NWL would not come up with a suitable means of supply. In those circumstances there was no need for the Secretary of State as competent authority to assess the effects it might have if it were ever proposed in the future.

We do not consider that the judge erred in refusing to grant permission to apply for judicial review, on either ground. He correctly concluded that the Secretary of State was entitled in this case to regard the project as the power station, and that the provision of a permanent water supply was not part of that project but formed a different and separate project. He was right to conclude that it was rational for the Secretary of State to defer appropriate assessment of the impact of the permanent water supply under regulation 63 of the Habitats Regulations to a later stage, because the information necessary for a proper assessment was not available at the time of his decision on the application for development consent for the power station. We therefore dismiss this appeal.