The British actor, who plays scheming servant Thomas in the hit period drama, pounded the pavements of the British capital along with 38,000 other runners to raise money for a multiple sclerosis centre in England.

James-Collier completed the epic feat in three hours and 43 minutes, and he also broke his fundraising target of $16,000 (£10,000) by bringing in more than $23,360 (£14,600) as WENN went to press.

He also shared a picture of himself holding his medal after crossing the finish line.

As part of his fundraising efforts, the actor enlisted his Downton Abbey co-stars to film a Star Wars spoof called Downton Wars Episode 1: The Phantom Valet, and he promised to release the second part, Downton Wars Part 2: The Evil Butler Strikes Back, when donations hit $16,000.

Other stars who turned out for the event on Sunday included David and Victoria Beckham, whose 12-year-old son Romeo competed in the children's mini-marathon, while veteran supermodel Christy Turlington and Formula One driver Jenson Button were among those competing in the full 26.4-mile (42.4-kilometre) endurance race.