Leaked report raises questions over UK grid security as Ofgem takes over investigation from NESO; whistleblower warns blackout is 'an engineering certainty'

A leaked internal report from the National Grid Electricity System Operator (NESO) has revealed that five transmission constraints were breached on June 23, with the largest breach reaching 700 MW. The report indicated that these breaches occurred with “no available pre or post-action mitigation options.”

A second report, described as a “NESO Significant Event Report,” confirmed that during the incident, system constraints were breached and system security was compromised. A whistleblower from NESO warned that a major blackout is “an engineering certainty,” raising serious concerns about the integrity of the grid.²³

Worryingly, the whistleblower claimed that NESO colleagues are “re-running the models” to alter data and calculations to present a secure version of the grid on June 23. In response to these alarming findings, Ofgem has taken over the investigation, effectively sidelining NESO executives from regular updates and initiating its own inquiry into security of supply concerns.

Ofgem's principal statutory objective is to protect the interests of existing and future consumers, and it must act to safeguard the public from dangers arising from electricity generation and supply. If credible allegations arise regarding incomplete or misleading operational data, Ofgem cannot simply rely on the organization concerned to respond. A recent government review of Ofgem concluded that its current structure and capabilities are insufficient for a complex and fast-changing energy system, necessitating “clearer responsibilities, stronger and more agile enforcement, and enhanced organisational capability to anticipate risks and act decisively.”