Heathrow appeared to be coping with the record influx of flyers, including various Olympic teams, ahead of the Games.
In total, the airport is handling around 217,000 passengers today, including 99,000 arrivals, on its busiest day to date.
Immigration queues for arriving passengers were reported to be moving smoothly.
More than 1,000 volunteers, speaking more than 20 languages between them, are welcoming groups of athletes and officials from their planes.
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The families of all four of the victims, all of whom were men, have been informed, police said.
A motorcyclist from Nottingham has died in an accident at the Macau Grand Prix in China, earlier today.