The factual account provided by NESO establishes the sequence of events and notable actions taken during the week and provides the foundation for the next phase of our work.

We have reviewed this report and set out our updated lines of enquiry to focus on key areas including the security of the system, operational planning and decision-making and interconnector flows. We will also consider demand forecasting, generation availability, balancing services and the response of the wider market.

At this stage, we have not drawn conclusions or made regulatory judgements about the events or actions set out in the preliminary report. In the coming months we will test the evidence through technical analysis, detailed examination of operational information and engagement with NESO, industry participants and other relevant stakeholders.

We aim to publish our conclusions on whether the GB electricity system remained secure during the June 2026 events and whether security standards were maintained, as soon as possible after receiving the final report and no later than 31 January 2027.

If our inquiry finds instances where there is material reason to believe a licensee has not complied with its obligations, then we will consider opening enforcement investigations. We will publish our conclusions on lessons learned from these events no later than 31 March 2027, setting out a clear, timebound plan of action to help ensure the sector is better prepared for any extreme heat periods in the future.

Independent investigation into the whistleblowing allegations

Separately, NESO has also published the findings of the independent Eversheds Sutherland investigation into whistleblowing allegations relating to operational decision-making and record-keeping during the same period. The investigation report raises important issues about working culture and practices at NESO, and we are pleased the NESO Board has said they will consider these carefully and set out a plan of action in response.

Ofgem was on the independent assurance panel that oversaw the process, represented by Akshay Kaul, Ofgem Director General for Infrastructure, alongside Jayne Scott, Chair of NESO’s Audit and Risk Committee, and Siobhan Duffy of UK Government Investments, to ensure the investigation was conducted objectively and independently.

Ofgem will carefully consider the findings of the Eversheds Sutherland investigation and any implications for its wider regulatory review. The two reviews are distinct, but relevant evidence from the independent investigation will inform Ofgem’s work.