An independent investigation into allegations that Britain’s electricity system operator concealed evidence of blackout risks during a June heatwave has found no evidence of wrongdoing, but raised concerns about the relationship between frontline engineers and senior management.
The investigation, conducted by law firm Eversheds Sutherland and published on 19 October, examined claims that staff at the National Energy System Operator (NESO) had been encouraged to alter or suppress operational records to avoid public scrutiny of difficulties in maintaining electricity system stability.1
Although the allegations were not substantiated, investigators identified cultural, governance and control issues requiring attention, including the handling of concerns raised by control room personnel.
The findings come as Britain’s electricity network faces increasing operational demands from the expansion of renewable generation, growing electricity consumption and the need to maintain system stability during extreme weather.
Concerns during June heatwave
The investigation followed allegations made public in July by Conservative MP Claire Coutinho, then shadow energy secretary, who said whistleblowers had raised concerns about the secure operation of the electricity system.
The claims related particularly to the period between 22 and 26 June, when unusually high temperatures placed additional demands on electricity infrastructure.
Investigators interviewed 36 witnesses across NESO and examined allegations concerning the management of operational records, documentation of decisions and possible interference by corporate affairs personnel.2
They found no evidence that records had been deliberately altered or concealed, or that communications staff had improperly influenced control room decisions.
However, the investigation identified significant pressures on operational personnel and a disconnect between engineers responsible for maintaining grid stability and senior executives. Staff concerns included whether operational difficulties were being sufficiently acknowledged by management.2 The report also identified inconsistent logging practices and gaps in version control, although investigators found no evidence that these shortcomings reflected a deliberate attempt to conceal information.
NESO has accepted the investigation’s recommendations in full and said its board will oversee their implementation.
Chief executive Fintan Slye said the findings identified opportunities to improve how staff concerns were raised and addressed.
“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.”
System security under scrutiny
A separate technical review commissioned by energy regulator Ofgem is examining the electricity system’s performance during the June heatwave.
A preliminary report published alongside the investigation established that system frequency remained within statutory limits of 49.5Hz to 50.5Hz throughout the period, and that no customers were disconnected.
Nevertheless, the operating conditions were challenging. On 23 June, system frequency fell below normal operational limits for an extended period, prompting measures including the suspension of electricity exports to the Netherlands. The combination of unusually high temperatures, lower wind generation and reduced availability from some generating assets created tighter operating margins than normal.3
Ofgem stressed that it had not yet reached regulatory conclusions about the events.
Its continuing investigation will examine system security, demand forecasting, generation availability, operational decisions, interconnector flows and the performance of balancing services.
The final technical report is expected in December, after which Ofgem will assess whether operational requirements were met and whether changes are necessary to strengthen resilience.
Debate over future grid resilience
The findings come amid wider debate about how Britain should manage an increasingly complex electricity system while pursuing its clean energy ambitions.
Christophe Williams, founder and chief executive of UK solar thermal technology company Naked Energy, said the investigation highlighted the need for greater investment in decentralised energy infrastructure.
“Although this report shows there is no evidence of a cover-up of blackout risks, it’s clear that blackouts are a very real concern for the staff at Neso. The issue isn’t too much renewable energy, it’s that our grid was never designed for a decentralised, electrified energy system.”
Williams argued that relying heavily on electrification to meet decarbonisation targets would place additional pressure on electricity networks, and called for wider deployment of technologies capable of meeting energy requirements locally.
He pointed to solar thermal systems, which generate useful heat directly from sunlight, as one way for businesses to reduce their dependence on grid-supplied energy.
“Investment in distributed energy systems that work alongside the grid will cut costs and accelerate the transition in concert with existing infrastructure,” he said.
The comments reflect a wider debate about the respective roles of network reinforcement, energy storage, demand flexibility and decentralised generation in supporting the transition to low-carbon energy.
However, the technical review has yet to establish the full circumstances of June’s operational difficulties, or whether any shortcomings in planning and system management contributed to the pressures experienced.
Ofgem aims to publish its conclusions on system security by 31 January 2027, with a further assessment of lessons learned due by 31 March.4
Notes
[1] Eversheds Sutherland, Whistleblowing Investigation: Final Report, 19 October 2026.
[2] NESO, Independent investigation concludes allegations against NESO were unsubstantiated, 19 October 2026.
[3] NESO, Review of Electricity System Operation during Extreme Heat 22–26 June 2026: Preliminary Report, published by Ofgem, 19 October 2026.
[4] Ofgem, Update on the Independent Eversheds investigation and Ofgem’s technical review of energy system operations during extreme heat, 19 October 2026.
