Paula Radcliffe hit the qualifying mark for London 2012 as she finished the Berlin marathon in third place, behind winner Florence Kiplagat, on Sunday.
Radcliffe, 37, posted a time of two hours, 23 minutes and 46 seconds, inside UK Athletics' qualifying standard of two hours 31 minutes.
"I should be happy and I'm a little annoyed but that gives me things to work on," Radcliffe told BBC Sport.
Scott Overall reached the British men's qualifying time as he finished an impressive fifth on his marathon debut, while Haile Gebrselassie failed to finish the race.
Overall, 28, ran 2:10.55 - more than a minute inside the qualifying mark of two hours 12 minutes demanded by UKA.
British world record holder Radcliffe was running her first marathon since the birth of her second child in 2009.
"I'm not happy because I would have liked to run faster, and win the race, but my main goal was to enjoy it and I kind-of did. I got a bit carried away," she said.
"I was thinking 'be sensible, get this tucked away, get the qualifying time and put the ego to one side'. I know I can get in a better shape for next year.
"Anybody who is healthy on the start line is in with a shot [of winning the Olympics]. My hip needs to rest a bit. I should be happy, but I'm not."
The qualifying time Radcliffe had to beat was well outside the best of 2:15.25 she set at the London marathon in 2003, but she had admitted to feeling "a bit of fear" ahead of the race given the years which had passed since she last competed.
With her finishing position less important than the time she achieved, Radcliffe let Kenya's Kiplagat slip away at the 15km mark and was 19 seconds back by the halfway stage.
Germany's Irina Mikitenko passed Radcliffe after 30km on her way to a second-place finish, but Radcliffe will be pleased to meet the London 2012 criteria.
Kiplagat won in a time of 2:19.44, outside the course record but the second-fastest time in the world this year.
"That's about the time you'd have guessed Paula could run if she was fit," said BBC Sport analyst Brendan Foster, an Olympic bronze medallist over 10,000m at Montreal 1976.
"Hopefully her injuries are now behind her. She's clearly demonstrated she's healthy again and this is a terrific step forward.
"She ran faster for the first 10k today than in the 10k race she ran in London earlier in the year. It is a huge boost for British athletics and the London Games because clearly she's going to be selected now."
Overall said: "I couldn't believe it. When I got to 40k I thought I had got the time wrong, so I was cruising on the home straight, and when I saw the clock said 2:10 I was very surprised.
"I was on my own from halfway and think that if I had a pacemaker possibly may have gone quicker. All in all, not a bad debut."
Britain's Ben Whitby finished 11th in the race with Andi Jones 21st.