A fire that shut Heathrow airport in March, stranding thousands of passengers, was caused by National Grid's failure to maintain an electricity substation, an official report said on Wednesday, prompting the energy watchdog to open a probe.

National Grid aware of fault behind Heathrow shutdown fire for seven years - National Grid blamed for failing to act on known transformer problem, while Heathrow accepted risk as a ‘high-impact, low-p

HEATHROW may sue the National Grid after a probe found a fault causing the huge substation fire was identified seven years ago. The blaze in March halted flights for 24 hours — affecting 270,000