Hayes substation fire

On the evening of 20 March 2025, a fire began at an electrical substation in Hayes, Hillingdon, London, leading to the closure of Heathrow Airport. The fire cut electricity supply to the airport which was not able to be managed by back-up systems and that led to more than 1,000 flights to and from the airport being cancelled and disrupted travel for around 200,000 passengers.^[1]

Airports are, typically, protected by an uninterruptible power supply (UPS).^[2] The site has been hit by thunderstorms before. The local substations were operated by SEB.

The substation was built by J. L. Eve Construction at North Hyde Gardens around 1967.^[3] Around the same time, an underground 275kV line was built to Iver Heath substation in Buckinghamshire, also built by J. L. Eve Construction in 1961.^[4]

On 20 March 2025, at 23:23 GMT, emergency services were called to a fire at North Hyde electrical substation in Nestles Avenue, Hayes, Hillingdon.^[5] Ten fire engines and 70 firefighters were dispatched^[6] as a 650-foot cordon was established.^[7] London Fire Brigade reported that one transformer within the substation was alight. By 04:00, half of a transformer remained on fire.^[8] Energy Secretary Ed Miliband told reporters that this was a 'catastrophic fire', which was 'unusual and unprecedented' which had also affected a backup generator.^[9] As of 13:00 on 21 March, the fire continued to burn at a reduced level, fuelled by 25,000 litres of cooling oil which had been contained within the burning transformer.^[10]

After the fire began, Heathrow Airport announced that it would be closed on 21 March, forcing 120 flights to be diverted to Gatwick Airport, Charles de Gaulle Airport, Shannon Airport, and Goose Bay Airport.^[11] Flightradar24 stated that at least 1,351 flights were affected. Cirium, an airplane analytics firm, estimated that 290,000 passengers would be affected.^[11] 1300 flights were expected to be affected assuming the airport could reopen at midnight the same day.^[9] Flights could not be diverted to other British airports due to lack of capacity, Heathrow being Britain's largest airport and an international hub.

Heathrow airport has some backup power supplies but these are inadequate to run the whole airport. There are two grid substations in the vicinity of the airport, to the north North Hyde and south Laleham, but it is only connected to the northern one. Only two UK airports have any regulation concerning their resilience to disruption, Heathrow and Gatwick Airport, but an October 2023 a report by the National Infrastructure Commission recommended government should set standards for resilience at important infrastructure sites including airports. Other important sites such as data centres, which use similar amounts of power as the airport typically have two grid sources of power plus generators and battery backup sufficient to ensure uninterrupted operation.^[12]

Heathrow is also an important cargo airport, carrying £190bn of goods per year, 48% of UK air cargo.^[13]

On 2 April, the shutdown of Heathrow Airport was the subject of a meeting of the House of Commons Transport Select Committee. Appearing before the Committee, Nigel Wicking, chief executive of Heathrow Airline Operators' Committee, a group representing airlines, said that he had raised concerns with Heathrow about the "resilience" of its power supply on two occasions in the week preceding the closure. But Thomas Woldbye, Heathrow's chief executive, described the closure as an "unlikely event" that required "very serious safety decisions".^[14]

A fire near the Heathrow station disrupted Heathrow Express and portions of the Elizabeth line.^[15] Trains and London Underground services to Heathrow were suspended or disrupted. The Motorway M4 was closed between junctions 3 and 4, while local roads were also closed affecting bus routes.^[10]

At least 150 people were evacuated,^[16] and at least 16,300 homes lost power.^[17] National Grid reported at 06:00 on 21 March that they had restored power to 62,000 customers, but 4,900 homes remained without power.^[10]

The preliminary National Energy System Operator investigation report, in May 2025, ruled out suspicious activity as the cause, but did not identify the root cause of the fire. The team had investigated 600 items of evidence relating to the 57 years old substation. The investigation will continue, including of the configuration of the private airport network, with a final report expected in June.^[18]

Heathrow airport held an internal investigation into resilience, led by Ruth Kelly, former government minister and airport board member.^[18] Its report stated that in the given circumstances, shutting down the airport was the correct decision due to safety, and that resilience efforts will continue.^[19]

In July 2025, NESO reported that National Grid had been aware of a fault in July 2018, but that it had not been repaired. Excess moisture levels were found in substation components, for which bushings should have been replaced. Ofgem announced that it would be investigating National Grid, which is responsible for the resilience of critical national energy infrastructure.^[20]

• On Friday 16 June 1989, Gatwick Airport had no electricity for two hours, after a transformer blew up after a power failure; the back up system did not work.^[21] Gatwick is likewise connected to two substations, with one at Smallfield Heath operated by SEEB.

• North Hyde Review Interim Report
• North Hyde Review Final Report

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