Mystery surrounding Heathrow fire that triggered airport power outage as cause of blaze unknown
8 May 2025, 08:52 | Updated: 8 May 2025, 12:35
The cause of a substation fire that triggered a total shutdown of Heathrow airport in March remains unknown, an investigation has found.
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The blaze, which ripped through an electrical substation around 1.5miles from the airport, caused a major power outage that affected swathes of the surrounding area - including Europe's biggest airport.
Heathrow "no choice but to close" for 16 hours following the outage, leading to the cancellation of 1,000 flights to and from the transport hub, with the knock on effects impacting hundreds of thousands of passengers.
The Met ruled out foul play in the hours that followed, with a statement released on March 25 noting officers had "found no evidence to suggest that the incident was suspicious in nature".
An investigation by National Energy System Operator (Neso) has found that power was restored to Heathrow airport's terminals seven hours before flights resumed on the day it was closed because of a substation fire.
An interim report by Neso found the flow of electricity to all four of the west London airport's passenger terminals was restarted by 10.56am on March 21.
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Flights did not resume until approximately 6pm, with Neso adding that power was restored to the "wider Heathrow Airport Limited network" by 2.23pm.
That was followed by "a period of safety checking" to ensure "safety-critical systems were fully operational prior to passengers arriving at the airport".
The investigation by the National Energy System Operator (Neso), has led to a review of the design standards of substations and resilience planning for national infrastructure.
The fire at the nearby North Hyde substation started late the previous evening.
A Heathrow spokesperson said: "Heathrow welcomes the Neso review's initial report, which raises important questions for National Grid and SSEN (Scottish and Southern Electricity Networks) 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."
Following the release of the investigations findings, Energy Secretary Ed Miliband has welcomed the interim report by the National Energy System Operator (Neso) into the Heathrow airport power outage.
He 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."
