The DCO was granted in 2022 and authorises the construction and operation of Sizewell C. In March 2025, the Secretary of State refused a request by a campaign group, Together Against Sizewell C Ltd., to vary or revoke the DCO, which had been made on the grounds that further flood protection for the power station, in the form of overland flood barriers, might be required at some point in the future, and which had not been subject to assessment under the Conservation of Habitats and Species Regulations 2017 when the DCO was granted.

After an oral hearing on 9 December 2025, Mr Justice Mould today handed down judgment refusing permission to apply for judicial review and certifying that the application was totally without merit. He held that it was unarguably open to the Secretary of State not to exercise his powers, given the fundamental uncertainty as to whether any such further flood protection would be required and the fact that the law allows for staged assessment in any event.

Hereward Phillpot KC and Hugh Flanagan acted for Sizewell C Limited, the Interested Party in the claim, instructed by Herbert Smith Freehills Kramer LLP.