The cause of a substation fire that sparked massive delays at Heathrow Airport is unknown, according to an interim report.
The National Energy System Operator (NESO) investigation revealed that power was restored to all four passenger terminals by 10.56am on March 21, yet flights didn’t restart until approximately 6pm that evening.
While electricity flowed back to the main airport network by 2.23pm, a subsequent period focused on safety checks ensured critical systems were fully operational before passengers were allowed to return.
More than 270,000 air passenger journeys were disrupted at Heathrow as Europe’s biggest airport had “no choice but to close” for 16 hours.
The fire at the North Hyde Substation, which supplies electricity to Heathrow about 1.5 miles away, started late the previous evening (March 20).
The cause of the fire remains unknown. The Metropolitan Police previously confirmed that officers had “found no evidence to suggest that the incident was suspicious in nature”.
Heathrow airport said the report raises “important questions” for National Grid – which owns the substation – and Scottish and Southern Electricity Networks (SSEN), which is responsible for power distribution in the area.
A spokesperson said: “Heathrow welcomes the Neso review’s initial report, which raises important questions for National Grid and SSEN that we hope the final report will provide answers to, including the cause of the fire.
“Further clarity on how the fire started and why two transformers were subsequently impacted can help ensure greater resilience for the UK’s energy grid moving forward.”
Energy Secretary Ed Miliband, who commissioned the report, said: “My department took immediate action to investigate the power loss, which impacted Heathrow and the surrounding area (on March 20 and 21), causing major disruption to thousands of people and many businesses.
“The National Energy System Operator’s initial summary of the incident rules out the possibility of any suspicious activity.
“We now await the full report to understand what happened and learn lessons to strengthen UK energy resilience and protect our critical national infrastructure.”
NESO stated the final report will be published in June. The body is expected to make key findings and recommendations on three core areas: the resilience of existing energy infrastructure, the response and restoration processes following disruptions, and the broader resilience of critical national infrastructure to energy-related issues.
