Energy watchdog Ofgem has launched an investigation after a new report found the fire, which broke out on March 20 in Hayes, west London, was due to a preventable technical fault.

The fire at an electrical substation was caused by a short circuit in a part that hadn’t been properly maintained by National Grid, an official report found.

Ofgem has launched an investigation into National Grid, it was announced on Wednesday, after a report found the fire that closed Heathrow earlier this year was caused by a known fault at an electricity substation.

An inquiry has found that an electrical substation fire that shut down Heathrow Airport in March was caused by a preventable technical fault identified almost seven years earlier.

A power outage which wiped out electricity to Heathrow airport and caused travel chaos for passengers could have been avoided, a new report has revealed.