Britain's Helen Jenkins saw her dream of Olympic gold end in disappointment as she finished fifth in the women's triathlon at a packed Hyde Park.
The Welshwoman went into the race as the reigning world champion and one of the favourites, and she was in contention until the last kilometre of the run, when she faded.
The gold medal was won by Switzerland's Nicola Spirig in a amazingly close finish from Sweden's Lisa Norden, with Erin Densham of Australia claiming the bronze.
Spirig and Norden crossed the line in exactly the same time but it was the Swiss athlete who was given the verdict on a photo finish.
Jenkins revealed afterwards she has been struggling with a right knee injury for the last 10 weeks since winning her most recent race in San Diego in May.
The 27-year-old from Bridgend said: "I've had an amazing team that got me to the startline. I didn't prepare as I would have liked, I maybe did 80% of what I wanted to. I just wasn't sure what my form was when I went onto the run.
"I was in a great position until 8km. The crowd was absolutely amazing. I think if they weren't there, I maybe would have been a bit further back, they really pushed me, but I got everything out of myself today.
"I've been training in pain for about 10 weeks now so it will be nice to have a break and try to let it heal. I tried not to think about it beforehand, you've got to be as strong as you can."
Britain have never won an Olympic medal in triathlon despite consistent success at world level, and to give Jenkins the best possible chance British Triathlon selected two athletes, Lucy Hall and Vicky Holland, to help their team-mate.
Hall, 20, is a relative novice at elite senior level but one of the fastest swimmers in the sport, and the plan was for her to lead out Jenkins and Holland.
Things did not go to plan, though, as Jenkins and Holland were left behind and Hall instead led out a small group onto the 43km bike ride.
Holland was then caught up in one of a number of crashes at the same corner outside Buckingham Palace and dropped back, but Jenkins' group caught the leaders and they rode as a pack of 22 until the second transition, with Hall doing a lot of the work.
Jenkins headed to the front at the start of the run and the lead group was gradually whittled down to four, before America's Sarah Groff impressively pulled herself back into contention.
And sadly for the home fans who lined the route 10 deep, the next to drop off was Jenkins, and there was no way back.
The 27-year-old added: "I'm so grateful to Vicky and Lucy, they put me in the right position but I just didn't have the legs on that last lap. The girls who got the medals, they really deserved that."
Holland crossed the line in 26th bloodied from her early fall and with regret that she did not do more to help Jenkins.
The Gloucester athlete, who trains in Swansea, said: "I'm just really disappointed, it meant I couldn't do the job I was put here to do. I wasn't here to run fast, I was here to do everything I could for Helen.
"There was a lot of pressure and a lot of expectation, especially with the team built around her. I think she feels that she's let us down but she hasn't. She gave everything.
"She's had an injury, she's pushed through. When we were training with her in Bridgend you could see she was doing run session upon run session in pain. You have an A plan, a B plan, a C plan, today was probably about a G plan."
Hall, from Lutterworth in Leicestershire, admitted she had got the tactics slightly wrong on the swim but was able to soak up the atmosphere as, her job done, she dropped down the field to finish 33rd.
The 20-year-old said: "In hindsight, I probably should have sighted a bit better to see where Helen and Vic were. I can't help but feel really upset for Helen because I know she's worked so hard over the last few years and I just really wanted her to get it.
"But I'm never going to do it again, a home Olympics, and I enjoyed every single minute of it. I couldn't hear myself think."
It is certainly not the end of Britain's triathlon medal hopes, though, with brothers Alistair and Jonny Brownlee going into Tuesday's men's race as the favourites for gold and silver.
Holland added: "We're going to be cheering even louder now to hope they get the luck that we didn't get today."