Independent investigation concludes allegations against NESO were unsubstantiated

An independent investigation into allegations raised about operational decision-making and record-keeping at NESO has concluded that there was no evidence to substantiate the allegations examined.

The investigation, conducted independently by Eversheds Sutherland (International) LLP, found no evidence of inappropriate influence over operational decisions and no evidence that control room records were altered, inappropriately managed or concealed, including to avoid public scrutiny.

The report did identify areas for improvement, particularly in how colleagues can raise concerns, how those concerns are heard and how feedback is provided. NESO has accepted the recommendations in full and is developing an implementation plan, delivery of which will be overseen by the Board.

The investigation was commissioned in July 2026 following allegations raised about operational decision-making and record-keeping during the period of extreme heat between 22 and 26 June 2026.

Its work was overseen by an independent panel chaired by Jayne Scott, Chair of NESO's Audit and Risk Committee, alongside Akshay Kaul, Ofgem Director General for Infrastructure, and Siobhan Duffy of UK Government Investments.

Paul Golby, Chair of NESO, said:

“These were serious allegations and the Board were explicit that they needed to be investigated independently and comprehensively. We are grateful to everyone who contributed to that work.

“The investigation’s findings are clear that there was no evidence to substantiate any of the allegations around inappropriate influence over decision making or inappropriate record keeping processes.

“The Board will oversee the development of plans to address the issues raised in the report and ensure these are implemented as a matter of urgency.”

Fintan Slye, Chief Executive of NESO, said:

“We welcome the findings of ESI’s independent and rigorous investigation. It helpfully identifies areas where we could improve how colleagues can raise concerns and how we respond to them. I want all colleagues at NESO to feel heard. We will act on the recommendations, working closely with our Trade Unions, and be open with colleagues about the progress we make.”

 View the investigation report

Separate Ofgem commissioned technical review

Today, Ofgem also published the preliminary report from the separate review into the operation of the electricity system and market during the period of extreme heat between 22 and 26 June 2026.

The review, commissioned by Ofgem, is examining how Great Britain's electricity system and market operated during that period, including system conditions, operational decisions and market activity.

The preliminary report sets out the evidence reviewed and the chronology established to date. It confirms frequency did not deviate outside statutory limits at any point. The review remains ongoing, with final conclusions, recommendations and lessons learned due to be set out in a final report.

Kayte O'Neill, Chief Operating Officer at NESO, said:

“NESO is committed to continuous improvement, and we welcome the preliminary report into the operation of the electricity system during the extreme heat at the end of June. This was a very challenging period for the power system in Great Britain, and for power systems around Europe. Our Control Room engineers did an outstanding job, ensuring that no customers were disconnected and the frequency always remained within statutory limits.

“The next phase of the review will undoubtedly provide further learnings for the operation of system and market. It will be important that these are adopted to strengthen the resilience of our energy system for future extreme events.”

View the preliminary report View the TOR of the review Ofgem update