A Heathrow spokesperson said: "Heathrow is experiencing a significant power outage across the airport due to a large fire at a nearby electrical substation.

"Whilst fire crews are responding to the incident, we do not have clarity on when power may be reliably restored.

"To maintain the safety of our passengers and colleagues, we have no choice but to close Heathrow until 23h59 on 21 March 2025.

"We expect significant disruption over the coming days and passengers should not travel to the airport under any circumstances until the airport reopens.

"We will provide an update when more information on the resumption of operations is available.

"We know this will be disappointing for passengers and we want to reassure that we are working as hard as possible to resolve the situation."