Team GB's Andrew Osagie finished eighth in the 800m final despite taking 0.71sec off his personal best.
Kenya's David Rudisha lit up the Olympic Stadium with a sensational victory, breaking his own world record in the process.
As London 2012 chairman and former Olympic 800m silver medallist Seb Coe looked on, Rudisha made the most of ideal conditions, storming through the first lap in 49.28 seconds and powering to the gold medal in one minute 40.91 seconds.
Amazingly, Osagie's time would have won gold at the last three Olympic Games, while it also took him fourth on the British all-time list behind Coe, Steve Cram and Peter Elliott.
Osagie, who has now improved his personal best seven times this season, said: "Oh wow, that was some race to be a part of. I would love to have been watching from the sidelines.
"I think an athlete like David Rudisha deserves so much respect, even though you're trying to beat him. And when he performs like that in the third round of an Olympic Games, there's not really many people that can beat him, but I am so happy I got to be a part of the Olympics this year. It was such a big achievement for me.
"To run a personal best in the final is unbelievable. I think any major championships I would have got a medal with that time. My aim this Games was to run 1:44 flat in the final and hopefully that was going to be enough to be up there. Unfortunately I've run a little bit quicker and finished right at the back of the field.
"It's just one of those things, next year I am going to come back, I'm going to be strong and faster. This is my first sort of international season where I've managed to last from May until the championship so it bodes well for the future for me.
"Going into this season my PB was 1:45:3 and I've now run 1:43.7. It's a big jump if you look at it like that, but I've always been there or thereabouts, working my way up this season."