Heathrow Airport lost power on Friday when a fire broke out nearby.

The power loss was caused by a blaze at an electricity substation in Hayes, west London, late on Thursday evening.

What caught fire?

A transformer at the substation caught fire.

London Fire Brigade Deputy Commissioner Jonathan Smith said: “The fire involved a transformer comprising 25,000 litres of its cooling oil fully alight.

“This created a major hazard owing to the still live high voltage equipment and the nature of an oil fuelled fire.”

What caused the fire?

It is not currently known what caused the blaze.

The Metropolitan Police said they are not treating the incident as suspicious, although the force warned that inquiries are ongoing.

Following that initial confirmation from the Met, the LFB announced its investigation will focus on the electrical distribution equipment.

How did the fire lead to Heathrow’s power outage?

Heathrow’s chief executive Thomas Woldbye explained to reporters that the airport has three substations, each with a backup transformer.

The fire broke out at one of the three substations where the backup transformer also failed, causing a loss of power to Heathrow.

Why did the airport have to close?

Mr Woldbye said that the airport can run on power from the two unaffected substations but that they had to “restructure the supply”.

“So we’re not out of power but we have to restructure our power supply,” he told the media.

“To do that we have to close down systems – that is safety procedure, we will not go around that.”

He added: “Two substations can run the airport but we need to re-engineer the structure of the power supply for all the terminals and that’s what we were doing during the day, and then we have to restart all the systems and that’s what we’ve done, and we now see operation coming back.”