Jemima Sumgong recovered from a fall to win the women's London Marathon as fellow Kenyan Eliud Kipchoge retained the men's title in the second-fastest time in history.
Sumgong, 31, banged her head when tripped by Ethiopian Aselefech Mergia as they approached a water station.
She rejoined the leading group before taking her first London title in two hours 22 minutes 58 seconds.
Kipchoge, 31, won in 2:03:04, only seven seconds outside the world record.
His time has been bettered only by Kenyan Dennis Kimetto, who ran 2:02:57 in 2014 in Berlin, which is acknowledged as a quicker course.
Marcel Hug of Switzerland won the men's wheelchair race ahead of Britain's Paralympic champion David Weir in third, while American Tatyana McFadden won the women's race for a fourth consecutive year.
The 36th London Marathon saw an estimated 39,698 runners line up for the 26.2-mile course.
- London Marathon: Live video, radio & text
- Six inspirational stories
- Make Your Move: The Couch to 5k Challenge?
Sumgong falls, Sumgong wins
Sumgong, who has been a runner-up in the Boston, Chicago and New York marathons, was in the front pack when she stumbled near the 22-mile mark.
Mergia clipped the back of Sumgong's heel, and it brought both of them down along with pre-race favourite Mary Keitany.
But Sumgong, despite showing signs of discomfort as she checked her head injury, caught the leaders before breaking clear.
She finished five seconds ahead of last year's winner Tigist Tufa of Ethiopia (02:23.03), with Kenyan Florence Kiplagat third in 2:23.39.
"When we were heading to the last 5km mark to take water, we made a mistake of maybe crossing each other," said Sumgong of her collision with Mergia.
"I was just concentrating on my running. It was very painful on my head, my shoulder and my knee. But I feel OK now. I enjoyed it."
'One of the greatest races in history'
Kipchoge was neck-and-neck with compatriot Stanley Biwott on the 24th mile, before the reigning champion burst forward to take the outright lead.
He raised his finger in celebration as he made the final turn, before realising just before the line that he could have broken Kimetto's world record and earned a substantial prize-money bonus.
Biwott was second in a personal best of 2:03:51, while Ethiopia's Kenenisa Bekele came third in 2:06:36.
BBC commentator and former 1500m world champion Steve Cram described the race as "one of the greatest in history".
Britons book Rio 2016 places
The London Marathon doubled up as an official British trial for the Olympics in Rio this summer.
Alyson Dixon and Sonia Samuels secured their places in Team GB by finishing as the top two British women.
Dixon was 13th in 2:31:52 and Samuels 14th - eight seconds behind - both having already achieved the Olympic qualification standard of 2:31:00.
London Marathon debutant Charlotte Purdue was 16th in 2:32:48 and could be awarded a discretionary Olympic berth.
Scotland's Callum Hawkins and Tsegai Tewelde also booked GB spots for Rio, finishing eighth in 2:10:52 and 12th in 2:12.23 respectively.
African Tewelde is from Eritrea and claimed asylum in Britain after competing in the 2008 World Cross Country Championships in Edinburgh.
Hawkins' elder brother Derek was 14th in 2:12:57 and, like Purdue, could be offered a discretionary place for Rio.