Britain's swimming medal hopes were dealt a major blow this morning when Ellen Gandy went out in the heats of the 200 metres butterfly.
Gandy had come to the London Olympics as one of the medal favourites.
The 20-year-old won silver at the World Championships in Shanghai last year and her form as well as her mature, quiet confidence, had given rise to optimism she may become the first British woman to claim an Olympic butterfly podium place.
The Melbourne-based swimmer faded dramatically on the final length though and finished fifth in her heat, 17th overall and one place outside qualification.
Two days ago Gandy finished eighth in the 100m final.
It was not all bad news for Britain this morning, Gandy's good friend Jemma Lowe made it through to the semi-finals in the same event, in third place overall, while Michael Jamieson set a British record as he and Andrew Willis impressed in the 200m breaststroke heats.
The men's 4x200m freestyle relay squad reached tonight's final.
Gandy's exit though was a real shock, with an Olympic medal the only one missing from her collection.
Qualification looked a formality until the final turn from which she emerged well down and clearly struggling, the tank obviously empty, down the last 50m as she touched in two minutes and 9.92 seconds.
That time was almost four seconds down on her swim in the same pool in March at the Olympic trials.
Today was reminiscent of the 2009 World Championships when Gandy entered as the world rankings leader but finished 15th over 200m and 16th in the shorter race.
A teary-eyed Gandy was at a loss to explain her performance today, saying: "I felt okay at the start but after 100m felt like I had been hit by a truck.
"I've been feeling fine, no health issues, I just don't know what happened."
Lowe, seventh in Shanghai last year, is a good friend of Gandy's, the pair having been close since the days of the Smart Track programme pioneered by former national performance director Bill Sweetenham.
Of Gandy, Lowe said: "She made the Olympic final in the 100m and that was brilliant, and she had a fantastic year last year.
"Everyone has ups and downs and I'm sure she gave it her best."
The Swansea ITC swimmer swam a measured race to touch in 2mins 7.15secs and is well capable of reaching the final.
Lowe said: "I'm really happy to make it into the next round, it's been pretty hard for me the last few days watching all my team-mates compete.
"I'm used to competing on the first day in the 100m. That's the best time I've done in the morning."