The British astronaut, who ran the course while strapped to a treadmill, saw roads pass under his feet in real time on an iPad.
The 44-year-old has set a new record for fastest marathon in orbit, Guinness World Records confirmed on Sunday.
Guinness World Records adjudicated Peake’s attempt via live video link at the European Astronaut Centre of ESA in Cologne.
The record for the fastest marathon in orbit by a female is held by Sunita Williams, who ran in a time of four hours and 24 minutes on April 16, 2007.
Head of records Marco Frigatt said: "Tim has captured the hearts and minds of the nation since his mission on-board the International Space Station began last year.
"His latest achievement is surely his greatest – running the fastest marathon in space, on the only day-off from his gruelling schedule is fantastic accomplishment.
"Tim is a true inspiration and someone we can all look up to. Literally.”
Ahead of today's race, the British astronaut tweeted this stunning photo of London.
A total of 69 fun runners are attempting to achieve Guinness World Records titles today – from giant dinosaurs to a four-man fire engine.
Not content with running the marathon himself, Peake also had time to launch the countdown for thousands of eager participants waiting to start the route in London.
Peake sent his fellow runners a good luck video message before a 10-second countdown to start the 36th race.
He ran the 26.2-mile course in three hours, 18 minutes and 50 seconds on earth back in 1999.
The astronaut has received a lot of praise for his challenge.
Back on Earth, the winner of this year's marathon, Jemima Sumgong, gave a life lesson in perseverance after she recovered from a nasty fall to go on and complete the course in just under two hours and 23 minutes.
Sumgong held her head after a sharp impact with the road when she was tripped by Ethiopian Aselefech Mergia as they approached a water station.
Eliud Kipchoge, also from Kenya, retained the men’s title, running the route just seven seconds short of the world record.
Marcel Hug of Switzerland won the men’s wheelchair race ahead of Britain’s Paralympic champion David Weir in third.
American Tatyana McFadden won the women’s race for a fourth consecutive year.
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