More than 38,000 runners, fundraisers and elite racers have lined up to take part in this year's London Marathon - making it the biggest in the event's history.
World record holder Paula Radcliffe, 41, completed her final competitive marathon, saying the "magic of the London Marathon" helped her through.
Marathon world record-holder Paula Radcliffe ran her last ever race today, finishing in an impressive 2:36:55.
She might have won the London Marathon three times in the past - once in a blistering 2:15:25 - but this time she was just happy to finish, to huge cheers from watching crowds.
"I didn't care about the time all the way round and I just wanted to thank as many people as possible," Radcliffe told the BBC.
"I went off way too fast and then it got more and more emotional. It was just amazing the whole way round."
She said the "magic of the London Marathon" helped her finish.
A runner who took part in the London Marathon completed 21 miles before realising the "slight pain" he felt was actually a broken hip.
The London Marathon brings together thousands of people raising money for charity - not to mention some rather unusual costumes.
Nearly 38,000 runners will hope to complete Sunday's London Marathon making it the biggest event in its 35-year history.