Video - London Marathon men's wheelchair finish
Australian Kurt Fearnley denied Britain's Dave Weir a fourth successive London Marathon wheelchair win after surging clear in the final straight.
Paralympic champion Fearnley gained revenge over Weir, who won in a similar sprint last year, in a course record one hour, 28 minutes and 57 seconds.
South African Ernst van Dyk, who joined Weir in an early break, finished third.
American Amanda McGrory beat defending champ Sandra Graf in the women's race, with Britain's Shelly Woods sixth.
Weir and Van Dyk - who won last weekend's Boston Marathon - moved clear early from a field widely considered one of the best ever in a wheelchair marathon.
I didn't get into my racing chair until late January so it's pretty good going
But Fearnley and hauled himself back into contention towards the half-way point, in the company of world record-holder Heinz Frei.
By the time the leaders reached the Embankment, 20 miles in, the leading group was down to three of Weir, Van Dyk and Fearnley, setting up another tense finish.
Weir, whose is stronger over shorter distances, said before the race that he would feel confident if he was in a bunch at the end.
But he could not match Fearnley's burst and sat up as the Australian came through the tape.
Interview - David Weir and Kurt Fearnley
Weir won four Paralympic medals in Beijing in September and blamed the time he took off afterwards for his lack of fitness.
"I had a bit of time out after Beijing so I've only had two months' preparation," he told BBC Sport.
"I didn't get into my racing chair until late January so it's pretty good going."
Fearnley added: "I'm glad to get the maiden win in but we'll be back next year, he'll be back and it'll be just as tough."
McGrory came through at the head of a group of six racers in the women's event and said she had never been in a sprint finish with more than half that number before.
It all started with a bribe - McGrory
"I hadn't planned on sprinting that soon. I saw some of the other women come up so i though, It's now or never," she said.
"It is fantastic to get London - it's such a big race and it's always good to win the big ones."
Woods, who won in London in 2007, was upbeat, saying: "Amanda was brilliant. It was such a tough but great race.
"I gave it my all out there, my arms were so heavy at the finish.
"I'm using these marathons to look to 2012. Competitive marathons and finishes are where I've been lacking because I've not had the experience."
Video - Women's wheelchair marathon finish