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.

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.

Energy watchdog Ofgem has launched an investigation after a report found a fire that caused the shutdown of Heathrow Airport was due to a preventable technical fault.