LONDON American swimmer Ryan Lochte made the biggest splash of the London Games so far by obliterating his compatriot Michael Phelps, the greatest swimmer in Olympic history, in the first of their eagerly awaited duels.
Phelps, unthinkably, finished without a medal in the 400 meters individual medley -- a fate shared in the men's road race by British favorite and world champion Mark Cavendish, outmaneuvered and upstaged in his quest for the home nation's first gold by Kazakhstan's Alexandre Vinokourov.
Sun Yang powered to China's first male swimming gold in the 400 meters freestyle and his 16-year-old compatriot Ye Shiwen won the women's 400m individual medley in a stunning world record time, putting China top of the medals table on the first full day of competition.
Phelps is bidding in London to become the most prolific Olympic medal winner in history, but may be yielding the position of world's best swimmer to Lochte after coming only fourth in the 400m individual medley, where Phelps set the current world record in 2008.
Having scraped into the final by 0.07 seconds, Phelps looked way off the pace as Lochte's silky power brought him home with time to spare. Phelps missed out on a medal at the Olympics for the first time since he was a 15-year-old at Sydney in 2000.
Cavendish, too, was left trailing when a star-studded British team led by Tour de France winner Bradley Wiggins controlled much of the race but failed in a frantic attempt to bridge a gap of nearly a minute to a breakaway pack and set up a win for the sprint specialist.
Vinokourov, who was banned for two years in 2007 for blood doping at the Tour de France, surged past Colombia's Rigoberto Uran on the final stretch in front of Buckingham Palace.
The veteran, in tears at the end, had announced he was quitting professional cycling after crashing out of the Tour de France last year, but could not resist the urge to get back on the bike for one last shot at glory this year.
Cavendish, winner of 23 stages of the Tour de France, was the only British track cyclist to go home empty-handed from Beijing, and had desperately hoped to set the home nation on the road to a best ever haul of Olympic golds.
Meanwhile China, top of the medal table for the first time four years ago in Beijing, laid down a huge marker with two golds in the Aquatics Centre, whose swooping roof echoes the shape of a manta ray or the arched back of a butterfly swimmer.
Sun Yang came within a whisker of breaking the world record to win the men's 400 meters freestyle final and became the first Chinese man to claim an Olympic swimming title.
South Korea's Park Tae-hwan, who won the event in Beijing four years ago, led for the first 300 meters at world record pace but finished second, having won an appeal against a false start just to compete in the final.
Sun is also the overwhelming favorite for the 1500 freestyle, the longest event in the pool, where he set the world record last year.
Another Chinese talent emerged in the shape of 16-year-old Ye Shiwen, who won gold by going more than a second under the world record and five seconds faster than her previous best.
Ye unleashed an incredible sprint over the concluding freestyle leg to surge clear of the favorite Elizabeth Beisel of the United States.
In doing so, she became the first woman to break a long-course world record since polyurethane bodysuits, which boosted buoyancy and triggered a slew of records, were banned in 2009.
China's Yi Siling had already become the first gold medalist of the Games in the 10-metre air rifle -- despite confessing to reporters: "For the first round and the last round I was very nervous and didn't know what I was doing."
Her compatriot Wang Mingjuan extended a 10-year unbeaten international record to win gold in the first women's weightlifting event of the London Games, the 48-kg weight division.
In the last event of the night in the pool, Australia took gold in the women's 4x100 meters freestyle relay, ahead of the Netherlands and the United States.
On a day of mixed fortunes for South Korea, Jin Jong-oh won the men's 10-metre air pistol shooting, but their men's archery team, who won gold at the last three Olympics and set new individual and team world records in an earlier round, were knocked out in the semi-final.
However, their conquerors, the top-ranked United States, then suffered a shock defeat in the final to unfancied Italy.
The Italians moved to second in the medal table with a further triumph in the fencing arena. Elisa Di Francisca led an Italian sweep in the women's individual foil, ahead of Arianna Errigo and three-times gold medalist Valentina Vezzali.
Brazil's Sarah Menezes took judo gold in the women's -48kg category by defeating reigning Olympic champion Romania's Alina Dumitru, while Russia's Arsen Galstyan won the men's -60kg.
At Wimbledon, where Roger Federer won his 17th grand slam earlier this month, the world number one survived a scare in his opening Olympic singles match against Colombia's Alejandro Falla before prevailing 6-3 5-7 6-3 to book a second-round place.
Seeking his first singles gold, Federer made extra work for himself by missing three match points when leading 6-3 5-3. In the women's event, Serena Williams breezed past Serbia's Jelena Jankovic, with U.S. first lady Michelle Obama cheering her on.
Albanian weightlifter Hysen Pulaku became the first to be ejected from the London Games after testing positive for an anabolic steroid.
"Of course it is always a sad day when a cheating athlete is caught," said International Olympic Committee spokesman Mark Adams. "I hope there will not be more.
Competition got under way on Saturday after a dizzying opening ceremony on Friday night that celebrated Britain's history and its humour, but also put the emphasis on inspiring a new generation of young athletes.
The message could have been meant for the 23-year-old Irish gymnast Kieran Behan, whose low scores did little to dent his excitement at competing in an Olympics after twice being told he would never walk again.
As a 10-year-old, and already two years into gymnastics training, Behan developed a tumour in his leg, and was confined to a wheelchair after suffering nerve damage in the operation.
He learned to walk again, got back in the gym, then at age 12 was back in a wheelchair after falling from the high bar onto his head. This time it took three years to get back in the gym - where he ruptured both anterior cruciate ligaments in his knee.
"I wasn't nervous, I was very emotional," he said after walking out to compete alongside the defending team champions China. "I didn't know what to think because I have been through so much and my family have been through so much and to actually walk out on that stage, to actually be able to walk, is something I never thought would happen ...
(Additional reporting by Julien Pretot, Kate Holton, Julian Linden, Patrick Johnston, Kylie MacLellan, Michael Holden)