Louis Smith won a dramatic gymnastics silver medal on the pommel horse, missing out on gold by the narrowest margin after his overall score tied with Krisztian Berki.
Both Smith and Berki scored 16.066 but the Hungarian was awarded the Olympic gold for a higher execution score.
GB team-mate Max Whitlock scored a superb 15.600 on his Olympic debut, handing the 19-year-old bronze.
Smith, 23, adds silver to the bronze medal he won at Beijing 2008.
That medal, achieved at the age of 19, made him the first Briton in a century to win an individual gymnastics medal.
There, his score tied with that of Croatia's Filip Ude and Smith came off worse, missing out on silver.
Four years later, with Smith the favourite for Olympic gold and the last to compete in the North Greenwich Arena, the same happened again. This time, arch-rival Berki took the spoils.
"Louis was under huge amounts of pressure and he had to deliver the goods. In fairness to him he increased the difficulty and to get the same score as the Olympic champion is just fantastic. We've come so far in the sport. We are now the strongest team in the world on the pommel horse. I cannot believe it. This is terrific for British gymnastics."
"It was tough. It's happened twice now, at two Olympic Games, being bumped down," he told BBC Sport.
"I guess I'm used to it now. But to come second against one of the best pommel-horse workers the world has ever seen? I'm a happy guy."
He could not have done more, losing out by a fraction in a battle between two greats of the discipline.
When scores are level in gymnastics, the mark awarded for execution - as opposed to difficulty, which is the other half - is counted first to break the tie.
Berki had a difficulty score of 6.9 and an execution score of 9.166, to Smith's higher difficulty of 7.0 but lower execution of 9.066.
The Hungarian's victory means he has still to lose to Smith in a major final, but Smith's relief at getting through his routine was palpable, having fallen in the same arena at the 2009 World Championships.
Smith did not watch Berki's routine, instead opting to continue his warm-up in the depths of the arena. When a rehearsal of his hardest routine did not go to plan, he opted for a slightly safer set of moves and was happy with his decision.
"I can't sit here with my face screwed up when I've got a silver at an Olympic Games. It's such a journey, not just for me but for every Olympic athlete," said Smith.
"To perform one of my hardest routines cleanly knowing all my friends and family have come to watch, regardless of what medal it won, was an amazing feeling.
"I said this final would be a clash of the titans if we both went through our routines, and getting the same score shows how close it was."
Whitlock kept his composure remarkably and went through a clean, strong routine in his first Olympic individual final. Not only did it pick up a medal, it hinted at a brighter future in four years' time.
"I'm so happy with how my first Olympics has gone, I couldn't ask for more," Whitlock said.
"To come second to Louis Smith, to start with, is really good. He was so close to that gold. He's upped his medal from bronze to silver and he should be really happy with it. He's done well."
Kristian Thomas and Beth Tweddle are Britain's remaining gymnastics hopes in the men's vault and women's uneven bars respectively. Both finals take place on Monday.