George Clooney will run the 2016 London Marathon after losing a bet with his friend, the former model Christy Turlington Burns, who completed the 26.2 mile course in under four hours on Sunday (April 26, 2015).

George ClooneyGeorge Clooney will run the London Marathon in 2016

Clooney had said he would compete in the event should the former Calvin Klein model finish in under four hours, and Burns clocked in at three hours 45 minutes, leaving the Oscar winning actor with no option but to put his name down for the 2016 edition.

More: George Clooney's 3am emails over terrible Monuments Men reviews

"Thinking about George running a marathon and having a good night's sleep before the race will help my time," Turlington Burns said before the race. She added: "The moment I cross the line, I want to go for a pint."

Clooney is a famous philanthropist and will no doubt run for one of his many causes. He founded Not On Our Watch, a charity that has donated millions of dollars to help those suffering in Darfur and elsewhere, and he was named United Nations Messenger of Peace in 2008 to help raise public awareness and support for the UN's global peacekeeping efforts.

More: George Clooney hits Comic-Con touting impressive Tomorrowland

Other celebrities taking part in this year's London Marathon included DJ Chris Evans, Formula One driver Jenson Button and the double Olympic winning gold medallist James Cracknell. 

It was the second bit of bad news for Clooney this week, who lost out on the rights to Paul Barrett's Law of the Jungle to his good friend Brad Pitt. Pitt's production company secured the film rights to the book about an epic fraud-marred Ecuadorian environmental suit against Chevron.