With the 2012 Olympics in London, I guess it's no surprise that Heathrow Airport saw a spike in airline passengers.
Though, interestingly enough, passenger numbers fell 400,000 during the actual Olympics since Brits stayed at home so the number of inward-bound travelers dipped, according to BBC which also reported today that the airport, the UK's busiest, is operating at close to capacity, with 471,341 flights during 2012, just below the legal limit of 480,000 a year.

(from the BBC article)