Wilson Kipsang and Mary Keitany secured an impressive Kenyan double by winning the men's and women's races at the 32nd London Marathon.
Kipsang led for the final seven miles and just missed out on the course record in running 2:04:44.
Keitany won for the
second successive year
with a time of 2:18:37.
Claire Hallissey was the first Briton to finish, in 11th place, and her time of 2:27:44 should be enough to earn Olympic selection ahead of Jo Pavey.
Mary Keitany wins London Marathon
Paula Radcliffe and Mara Yamauchi have already qualified for this summer's Games, but Hallissey's time was quicker than Pavey, who did not run but had been ranked third.
"I'm keeping my fingers crossed," Hallissey told BBC Radio 5 live. "It would be fantastic (to qualify for London 2012). The home Olympics is the chance of a lifetime.
"I knew we were on target (but) it wasn't until I got to the clock with 800m to go that I knew for certain.
"I was running as fast as I could, so it was not worth the effort working out what time to go for."
Pavey, meanwhile, accepts she is likely to miss out in Tuesday's team announcement but thinks she can still make an impression in the 10,000m this summer.
She said: "There is a chance that they (the selectors) might take into account I ran a good time in New York on a hilly course but I think that won't be the case. I am not holding my hopes up for that.
"I'll turn my attention to trying to qualify on the track - that's what I am most familiar with. It's only the situation I am normally in every summer."
"They were two fantastic but contrasting Kenyan wins. Both Kipsang and Keitany will be favourites to triumph again at the Olympics in London.
"The results shows wonderful depth in British women marathoners as Claire Hallissey and Freya Murray move into the UK all-time top 10 list."
In the men's race, Lee Merrien was the first Briton to cross the line, finishing 17th.
The Guernsey athlete was on course to meet the Olympic 'A' standard of 2:12:00 but ultimately failed to make the mark despite setting a personal best time.
Merrien told BBC Sport: "I'm pretty gutted. I'm very disappointed.
"After three or four miles we were 100 yards behind the pacemakers and, from six and seven miles, I was forcing the pace at the front of the group and did a lot of the work.
"From halfway I was on my own for the rest of the race and I knew I was still at 2:12 pace but had to pick it up, and to do that on your own and into the wind was tough.
"I was just trying to take the atmosphere in towards the end because this might be the closest I get to the Olympics."
Scott Overall, who is the only British man selected for the Olympics after finishing fifth in Berlin last year, was acting as a pacemaker for his compatriots but pulled out after 15 kilometres with a minor hamstring strain.
Weir wins record-equalling sixth London marathon
Kipsang's dogged performance saw him finish more than two minutes clear of fellow countryman Martin Lel, who finished second, and 2010 winner Tsegaye Kebede.
"I knew when I went away they have to work very, very hard to beat me as I was feeling very good in myself," said Kipsang.
"I am sorry I didn't (break) the record but winning is the most important thing for me. I feel a little tired now, but I am happy and tired."
Keitany set a relentless pace to pull away from compatriot Edna Kiplagat in the final three miles and win by more than a minute, with Ethiopian Priscah Jeptoo coming in third.
She set a new personal best and Kenyan record on the way to defending her crown. Only Radcliffe and Russian Liliya Shobukhova have run faster.
Keitany said: "I'm pleased with my run and the time was ok. The weather here all week has not been good but when I saw the sunshine this morning, I knew the weather would be right for me."
More than 37,000 runners started the race.
MEN'S RACE RESULTS
1 Wilson Kipsang (KEN) 2:04:44
2 Martin Lel (KEN) 2:06:51
3 Tsegaye Kebede (ETH) 2:06:52
Top British finishers:
17 Lee Merrien 2:13:41
19 John Beattie 2:16:38
20 Phil Anthony 2:16:40
WOMEN'S RACE RESULTS
1 Mary Keitany (KEN) 2:18:37
2 Edna Kiplagat (KEN) 2:19:50
3 Priscah Jeptoo (KEN) 2:20:14
Top British finishers:
11 Claire Hallissey 2:27:44
13 Freya Murray 2:28:10
16 Louise Damen 2:31:37
19 Sonia Samuels 2:33:41
20 Amy Whitehead 2.33.44
21 Helen Decker 2:34:11
24 Alyson Dixon 2:35:46
25 Susan Partridge 2:37:41
26 Liz Yelling 2:40:08
27 Michelle Ross-Cope 2:49:18