Heathrow airport returned to normal business on Sunday, two days after it was forced to close when a fire at an electrical substation caused a power cut. Europe’s busiest airport had more than 1,000 flights cancelled on Friday after the fire at the substation in Hayes, west London. Flights restarted on Saturday, with the airport reporting more than 250,000 passengers used the airport. Arrivals and departures continued on Sunday, although a number of flights ran with slight delays in taking off. Energy secretary Ed Miliband has ordered the National Energy System Operator (Neso) to investigate the power outage. An internal