Hayes substation fire

The 275kV substation was built by J. L. Eve Construction at North Hyde Gardens around 1967. Around the same time, an underground 275kV line was built to Iver Heath substation in Buckinghamshire. The North Hyde site is part of the UK's National Grid. It is close to Heathrow Airport but outside its perimeter, and supplies a nearby 66kV substation operated by SSEN. ==Fire==

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. Ten fire engines and 70 firefighters were dispatched as a 650-foot cordon was established. London Fire Brigade reported that one transformer within the substation was alight. By 04:00, half of a transformer remained on fire, and the fire brigade had the fire under control by around 06:30. At 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. ==Impact==

Heathrow Airport About 90 minutes after the power outage began, Flightradar24 stated that at least 1,351 flights were affected. Cirium, an airplane analytics firm, estimated that 290,000 passengers would be affected. Heathrow management understood that they had a resilient power supply since the airport took power from three substations (North Hyde, Iver Heath, and another), and each substation had more than one transformer and was connected to the airport by more than one cable. In the event, the extent of damage at North Hyde and the need to isolate that site for firefighting meant that around a third of the airport lost supply. The affected area included Terminal 2, Terminal 4 and the road tunnel leading to the central area, which is the main route for passengers to access Terminal 3. It was possible to reconfigure the supply within the airport but the entire process for this – powering down, switching 33kV connections, powering up and testing systems – took up to 12 hours. Heathrow is also an important cargo airport, carrying £190bn of goods per year, 48% of UK air cargo. 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. Thomas Woldbye, Heathrow's chief executive, described the closure as an "unlikely event" that required "very serious safety decisions". Other transport The fire was close to the Great Western Main Line, near Hayes & Harlington station, and disrupted Heathrow Express services and portions of the Elizabeth line. Trains and London Underground services to Heathrow were suspended or disrupted. The M4 motorway was closed for a time between junctions 3 and 4, while local roads were also closed, affecting bus routes. and at least 16,300 homes lost power. 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. ==Investigations==

The preliminary National Energy System Operator (NESO) 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. Heathrow airport held an internal investigation into resilience, led by Ruth Kelly, former government minister and airport board member. In July 2025, NESO reported that National Grid had become 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. and that National Grid was not aware that the loss of one of Heathrow's three supplies would cause outages of the airport's critical systems. ==Similar incidents==

• 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. ==References==