Michael Jamieson produced the swim of his life to take Olympic 200m breaststroke silver and smash his own British record.
Only a new world record from Hungary's Daniel Gyurta could deny the 23-year-old gold, while Japan's Ryo Tateishi took bronze.
Jamieson, in his debut Olympics, came charging down the final 50m to deafening noise in the Aquatics Centre and closed right up on Gyurta.
But the 2011 world champion held on to touch in 2 mins 07.28 secs, just 15 hundredths of a second ahead of the fast-finishing Glaswegian and clear of Tateishi's 2:08.29.
Jamieson's compatriot and training partner Andrew Willis was in the medal mix at 150m but paid for his efforts late on to finish down in eighth.
Double Olympic champion Kosuke Kitajima of Japan, aiming to be the first man in Olympic swimming history to win the same event at three consecutive Games, could only finish fourth.
But Jamieson's surprise medal - he was only fifth at last year's World Championships, and second at the British Championships earlier this year - brought the best noise of the Games so far from the packed stands.
Britain's swimmers have under-performed at these Olympics so far, with just Rebecca Adlington's 400m freestyle bronze to show from the first five days of competition.
Jamieson, who came to London as far more of a medal outsider than some of his more illustrious team-mates and set a new British record in his heat, could never be accused of the same crime.
He said afterwards: "I loved it. I had a little more to give after last night. It's so much easier to swim with a bit of confidence behind you.
"I cannot believe I have got 2:07, but I forgot about the time tonight - it was more tactical. I tried to stay on Gyurta's shoulder for the first hundred. I wanted to have everything on the line.
"I was desperate to get on the podium tonight to repay the faith and support we've had. After last night I thought I could win it but he was too strong in the end.
"I had planned for this night and that helped with the nerves beforehand. For so many years I have gone over this in my head.
"I couldn't have done any more. It was everything I hoped it would be - the crowd bringing me down the final 50m was the greatest experience of my life."
Jamieson's medal was the first by a British male in the pool at an Olympics since Steve Parry took 200m butterfly bronze in Athens in 2004.
And when he stood on the podium in front of his home crowd, which included Prince Harry and comedian turned charity swimmer David Walliams, the 17,000-strong support roared their appreciation.
With Adlington's preferred event, the 800m freestyle, still to come in the pool, Great Britain could yet match the three medals they won indoors in Beijing four years ago. The team's other three medals at the last Olympics came in the open-water events.