Jess Andrews smashed her personal best by 83 seconds to win the British 10,000m trials and qualify for the Rio Olympics as Jo Pavey struggled.
The unheralded Andrews, 23, had run the distance only once before on the track.
Beth Potter is also on her way to Brazil after holding off Kate Avery to be the second Briton home.
Pavey, 42, finished sixth and must now chase a faster time and hope she is handed the discretionary third place in the team to reach a fifth Olympics.
Pavey, the 2014 European 10,000m champion, had been struggling with a chest infection over the past fortnight and only decided to compete at the last minute.
But Andrews, who was given financial support by Mo Farah’s foundation as a student, not only came through a packed field to see off the best athletes in Britain but stormed past Kenya’s 2009 world champion Linet Masai to take the overall win in 31 minutes 58 seconds.
That was both inside the GB qualification time by 17 seconds and blew away her only previous track mark of 33:21.23.
Andrews, who is engaged to Irish road cyclist and Olympic contender Dan Martin, told BBC Sport: “Everyone dreams of the Olympics. But it’s whether you’re dreaming about the reality, or whether you think, ah, it’s a dream, it’s never going to happen.
“I’m still a little bit shell-shocked. I’ve been training really hard, crazy hard, and I believed it was going to be my day.
“It’s weird – I’d had vibes in training, thinking I was feeling really good, and I had nothing to lose.”
Pavey’s hopes are not quite over, but after running 33:22.76 she must now get under 32:15 and hope the selectors give her the nod ahead of Kate Avery, the third Briton home in 32:11.84.
She said: “It was a real gamble to run – you feel bad making excuses but even yesterday I wasn’t sure if I was going to travel up.
“I wanted to give it a go, but I could tell after a few laps it wasn’t going to be there tonight.
“I could try to get a time somewhere but that might be tough, looking at the times the girls have run. I might have to refocus on the 5,000m, but I haven’t given up yet.
“There are so many good girls in both the 5,000m and 10,000m so it’s a really tough year, but I’ll keep trying for now and see what I can do.”
Meanwhile Andy Vernon, European silver medallist two summers ago, must also hope the selectors give him another chance.
While Farah is pre-qualified, Vernon has the qualifying time but was beaten by both Ross Millington and Dewi Griffiths in the men’s elite race.
He told BBC Sport: “I’m so disappointed – I did my best, but I had limited time to prepare given the last eight months I’ve had.
“If it had been in a month’s time it might have been a different scenario – I don’t like to make excuses, but it’s the truth.
“I wasn’t quite ready tonight, but hopefully I will be in two months’ time if I’m on that plane.”