Kat Driscoll secured an Olympic trampoline place for Great Britain after an eight-hour wait during World Championship qualifying in Birmingham.
Needing a top-eight place to secure GB an Olympic spot and qualify for the individual final, the world number one, 25, finished seventh.
After competing at 1100 GMT, Driscoll watched on as others tried to oust her.
"Knowing we've secured that spot and I'm in my first Worlds final is fantastic," Driscoll told BBC Sport.
Though she finished ninth overall, nations may only send a maximum of two competitors to the Games and, as China had four athletes in the top eight, Driscoll was elevated to seventh.
"Without a doubt, it's been the most horrific day of my life. [The wait] was awful.
"When I got off I was disappointed with how I'd competed - I didn't think my score would be competitive - but as the day went on I didn't know where to sit, I wanted to cry all the time and I wanted to be sick. The feeling now makes it worthwhile."
Though Driscoll is top of the world rankings, top trampolinists from the likes of China and Canada do not compete in as many ranking events.
As a result, the field at this event is by far the strongest of the year and a dozen or more women could easily have finished in the top eight.
A minor slip in the second of Driscoll's two qualifying routines dropped her score to 98.765, below the 100-point mark she had hoped to exceed.
Having posted her score early in the qualifying competition, the Tyne and Wear star then had to endure eight hours in which subsequent rivals tried to unseat her.
Portugal's Ana Rente and Japan's Ayano Kishi, the last two to go and both capable of knocking Driscoll out of the reckoning, failed to match her score and left the Briton sobbing in the arms of her husband as the Olympic place was confirmed.
For Somerset's Laura Gallagher, 22, it was a different story. She qualified ninth, one place outside the final, a result which means Britain can no longer have the maximum of two female trampolinists at London 2012 - a slightly unexpected setback for the team.
"I can't really describe it. It was really disappointing, and then to be so close and miss out by one place is devastating," said Gallagher, who scored 98.290 to miss Sunday's individual final - and an Olympic place - by 0.155 marks.
"It's horrible, but I'm really pleased for Kat."
Driscoll is not guaranteed to take up the spot at the Games she has earned here as Olympic trials next spring will confirm the name Britain puts forward, though she is the clear front-runner.
Britain's men failed to qualify for any places at the Games, Luke Strong posting the team's highest finish (31st) ahead of Jack Helme (39th) as Nathan Bailey and James Higgins had disappointing outings.
January's Olympic test event, at London's O2 Arena, was expected to offer the men a final opportunity for Olympic qualification. However, world governing body the FIG later suggested that no British male had earned the right to compete there. A full decision is expected by the end of the month.
The women have reached Friday's team final as the combined scores of Driscoll, Gallagher and Emma Smith (14th in qualifying) propelled them into third overall, behind China and Canada.
"We have mixed feelings about today," said Tim Jones, the British Gymnastics performance director.
"Our aspirations were to secure at least a couple of places for the 2012 Olympics. We have four strong women and it has been a solid day of performances but I think we probably would have hoped one of them would have shone in qualification.
"Whilst not distracting from Kat's performance in making the final, which was a terrific achievement, it probably wasn't the performance everybody was looking for."