Heathrow Airport is weighing legal action against National Grid after an official investigation concluded that a fire at a key substation—causing a near-total shutdown of the UK’s busiest airport—stemmed from a known and unresolved fault.
The March 21 fire, which led to the cancellation of over 1,000 flights and disrupted more than 270,000 passenger journeys, originated at the North Hyde substation that supplies power to Heathrow. According to a 77-page report from the National Energy System Operator (NESO), the cause was moisture accumulation in a component known as a bushing—an insulated electrical connector—first flagged by National Grid in 2018.
The report noted that moisture levels detected seven years earlier had reached thresholds considered by National Grid’s own guidance to indicate an “imminent fault.” Despite this, planned maintenance in 2022 was deferred, and repeated attempts to schedule repairs in subsequent years were unsuccessful.
Heathrow officials said the fire and resulting power outage inflicted “significant damage and loss” on the airport and airlines and accused National Grid of failing to act on preventable issues. In a statement to the BBC, Heathrow said the company “could and should” have taken responsibility to prevent the fire and said it expected National Grid to “take accountability for those failings.”
National Grid responded by acknowledging the incident as rare and stated it has since launched a comprehensive review of its infrastructure resilience, especially for substations serving critical infrastructure. It said it would cooperate fully with Ofgem, the UK’s energy regulator, which has launched its own investigation into the outage.
“The electricity network in Britain is among the most reliable in the world,” a spokesperson for National Grid said, adding that it has begun re-testing substations tied to vital infrastructure.
The fallout from the power failure has raised broader concerns about the resilience of the UK’s infrastructure and communications between energy providers and critical facilities. NESO’s report revealed that while National Grid knew the substation served Heathrow, it was unaware that the airport would be forced to shut down if power from the site was disrupted. The report also stated that current regulations do not require energy companies to know which of their customers qualify as “critical national infrastructure.”
Fintan Slye, CEO of NESO, characterized the incident as one of “missed opportunities,” noting that prompt maintenance after the initial moisture detection could likely have prevented the fire. He added that Heathrow’s own power systems lacked the flexibility to switch to backup connections quickly, contributing to the lengthy airport shutdown.
Heathrow has since pledged to implement 28 measures to improve its power resilience but reiterated its criticism of National Grid.
“A combination of outdated regulation, inadequate safety mechanisms, and National Grid’s failure to maintain its infrastructure led to this catastrophic power outage,” said Weston Macklem, head of media at Heathrow.
The incident not only disrupted airport operations but also impacted surrounding infrastructure, including roads, rail systems, and Hillingdon Hospital. Industry estimates suggest the cost to airlines may have reached as much as £100 million.
With input from BBC and the New York Times.
