Fault behind Heathrow fire was known about in 2018

Friday 21 March was a miserable day for more than 200,000 airline passengers who were planning to fly to or from London Heathrow airport. The UK’s busiest airport closed down almost completely for the day due to a fire at an electricity substation that provides Heathrow with power.

- SIMON CALDER TRAVEL CORRESPONDENT

What went wrong - and could it happen again? The National Energy System Operator (Neso) has just published its final report into the incident. National Grid is blamed for the fire that triggered the power outage. But the report also says Heathrow was aware that such an incident would have serious consequences, and that the airport accepted the risk as a “highimpact, low-probability event”.

These are the key questions and answers.

How did events unfold?

At 11.21pm on Thursday 20 March, a “supergrid transformer” at North Hyde substation near Heathrow caught fire and shut down. An adjacent transformer that had been “running on hot standby” switched into service, according to Neso, “with no interruption of supply to customers”. But as the fire spread, within 28 minutes all power from the substation was lost - affecting 71,655 customers, including Heathrow airport.

The power cut at the airport hit Terminal 2, parts of Terminal 4 and the access tunnel to Terminals 2 and 3 - “critical parts of the infrastructure”, according to Heathrow’s chief executive, Thomas Woldbye. He said that power was also lost to “buildings that house systems that are airport-wide, such as CCTV, some of the fuelling safety systems, and security locking systems for doors”.

Mr Woldbye was uncontactable at the time of the fire because his phone was switched to silent. In the early hours of Friday morning the chief operating officer, Javier Echave, took the decision to close Heathrow on safety grounds - despite the devastating emotional and economic consequences. The airport later said the decision was the correct one and that the CEO would have made the same call.