Alexandre Vinokourov of Kazakhstan dashed Great Britain's hopes of a perfect start to their home Olympics as he won the gold medal in the men's road race.
Mark Cavendish, the world champion and winner of 23 Tour de France stages, was the favourite for the 250-kilometre event, which included nine ascents of Surrey's Box Hill.
But despite phenomenal support from his four British team-mates - Team Sky trio Bradley Wiggins, winner of the Tour de France a week earlier, Ian Stannard and Chris Froome plus Garmin-Sharp's David Millar - a late breakaway went clear on the last of the climbs and those 32 riders were able to hold the Team GB-led peloton at bay.
Vinokourov and Colombia's Rigoberto Urán, a Team Sky colleague of Cavendish's, then gave their fellow escapees the slip inside the final 10km and they had it between them coming down The Mall.
Vinokourov pounced when Urán looked over his shoulder at the riders behind and that settled it, with Norway's Alexander Kristoff in third.
Cavendish, who had targeted Olympic glory ever since he became world champion last September, came home in the main bunch, 40 seconds behind.
"It's unbelievable - I felt tired but I said to myself 'I must go'", said Vinokourov, who is set to retire at the end of this season.
"I followed a big group but I knew I must attack. I knew if we arrived in a sprint I had no chance. I did a good job with Urán and we worked hard together. It's an incredible victory to finish my career."
In stark contrast to Vinokourov's jubilation, disappointment was etched on Cavendish's face, though he was rightly proud of the efforts his team-mates had put in.
He said: "They were incredible. I couldn't be more proud of them. They are absolutely spent. They rode 250km going 60kph for the last hour.
"We can't make excuses. We did everything as we said we'd do it and more. To see the guys and the calibre they have to be riding like that.
"We knew it was going to be like that coming into it. We said we'd just do our race as we wanted to do it and just see what happens.
"It seems like most teams are happy not to win as long as we don't. That's the story of our life now in cycling. It shows what a strong nation we are and we've got to take the positives from that and take it as a compliment. But it's bitterly disappointing."
Cavendish also hailed the home support as more than a million people took to the streets to make it the most-watched Olympic event in history.
He added: "Our ears are ringing. We just hear the noise and it was tremendous the whole way around. It's something I'll remember for ever."
Fending off attacks
The day had earlier seen a 12-man escape group go clear but despite that and rivals attacking all around them on the ascents of Box Hill, Great Britain remained calm, riding at Cavendish's tempo on the climb and at high pace on the descents and the flat.
The composition of the leading group altered, but Cavendish and his British team-mates passed the summit of Box Hill for the final time with a deficit of one minute 23 seconds to solo leader Philippe Gilbert of Belgium.
Gilbert was caught as the group of 32 formed at the start of the long run-in to the finish and they established a lead of around one minute.
Riders appeared unwilling to take the initiative and there was a crash in the leading group in Richmond Park as Fabian Cancellara veered into the roadside barriers.
Vinokourov and Urán then broke clear in the finale and the Kazakh launched his sprint with 400 metres to go, catching the Colombian by surprise, to triumph.