08-05-2025
Cause of Heathrow fire unknown despite six-week investigation
The cause of a substation fire which triggered the shut down of Heathrow airport remains unknown despite a six-week inquiry, according to an interim report.
A preliminary report by Britain's energy system operator said forensic work was still under way into the incident which saw 270,000 passengers stranded in March. However, it added that police had 'found no evidence to suggest that the incident was suspicious in nature'.
Around 1,300 flights were cancelled following the fire which happened just before midnight on March 20. It took almost 24 hours for the airport to be up and running again.
However, the report by the National Energy System Operator (Neso) found power was restored to Heathrow airport's terminals seven hours before flights resumed on the day it was closed.
The flow of electricity to all four of the west London airport's passenger terminals was restarted by 10.56am on March 21. Flights did not resume until approximately 6pm.
Neso said power was restored to the 'wider Heathrow Airport Limited network' by 2.23pm which was followed by 'a period of safety checking' to ensure 'safety-critical systems were fully operational prior to passengers arriving at the airport'.
The fire happened at the North Hyde substation in Hounslow causing its transformers to shut down, cutting power to part of Heathrow and around 66,000 properties in the surrounding area.
The inquiry since then has focused partly on the cause of the fire but also on why a fire in a single substation could have caused the whole of Heathrow to shut down.
A Heathrow spokesman 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.'
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