Heathrow Airport is considering legal action against National Grid after a report found the fire which caused the airport to shut down was a result of a known fault at an electrical substation.

An investigation found that National Grid, which owns the substation which supplies Heathrow, had been aware of a problem since 2018 but failed to fix it.

There were numerous opportunities to rectify moisture affecting electrical parts at the North Hyde substation, but maintenance was repeatedly deferred, the report said.

Heathrow told the BBC National Grid “could and should” have prevented the fire and that it expected it to “take accountability for those failings”.