LONDON, March 21 (Reuters) - Britain’s Heathrow Airport was shut on Friday after a huge fire at a nearby electrical substation wiped out its power, disrupting flight schedules around the world.

Around 70 firefighters were tackling the blaze in the west of London, which led to a mass power outage at Heathrow, Europe’s busiest and the world’s fifth-busiest airport, and also knocked out its back-up power system.