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

Where a proposed alteration to an authorised development remains fundamentally uncertain, with no firm proposal or sufficiently identifiable design, the competent authority may lawfully defer appropriate assessment until a later consent stage. The precautionary principle does not require assessment of speculative infrastructure whose need, timing, scale and design cannot yet be established.

A Secretary of State may therefore decline to exercise statutory powers to change or revoke a development consent order where the alleged change is inchoate and can be addressed through a later change application. The decision must still give proper, intelligible and adequate reasons and comply with the duty of proper inquiry.

The claimant, a campaign group opposing the Sizewell C project, sought permission to challenge the Minister’s refusal to exercise powers under the Planning Act 2008 to change or revoke the Sizewell C (Nuclear Generating Station) Order 2022.

The claimant relied on an Office for Nuclear Regulation report referring to possible future overland flood barriers if climate change produced sea-level effects worse than reasonably foreseeable. It argued that the barriers formed part of the project and had not been subject to appropriate assessment under the Conservation of Habitats and Species Regulations 2017.

The central issues were whether the Secretary of State had to undertake further assessment immediately, whether he had unlawfully failed to exercise his Schedule 6 powers, and whether his reasons and inquiry were legally adequate.

1. Permission refused. The claim was certified as totally without merit. The application was refused.
2. Under paragraph 3 of Schedule 6 to the Planning Act 2008, the Secretary of State could change or revoke the order where the statutory conditions were met. The present material did not establish that the authorised project included overland flood barriers. The report contemplated barriers only if future climate change proved worse than reasonably foreseeable, with their need, scale, location and design unknown for several decades.
3. The Secretary of State was not presently under a duty under regulation 9(3) of the Conservation of Habitats and Species Regulations 2017 to undertake a further assessment in respect of speculative barriers. If an application were later made to add them to the authorised project, the Secretary of State would then have to consider the duty under regulation 9(3) and the need for appropriate assessment under regulation 63, including intra-project in-combination effects and impacts on protected sites.
4. The staged approach was lawful. The Court of Appeal’s reasoning in the earlier Sizewell litigation, applying the precautionary principle, recognised that cumulative effects may be assessed at the later consenting stage where they cannot yet be sufficiently identified. That reasoning applied because there was no firm proposal for the barriers.
5. The Minister’s reasons were proper, intelligible and adequate. There was no arguable breach of the Tameside duty of proper inquiry, nor any arguable breach of the environmental assessment duties. The claimant’s premise that the barriers were a fundamental and presently assessable part of the project was unsustainable.

The judgment states that an earlier judicial review challenge by the claimant was refused permission in this court and on appeal. The Court of Appeal decision was reported as [2023] EWCA Civ 1517; [2024] ELR 22. This judgment concerned a later application for permission to challenge the Minister’s letter of 28 March 2025.