Lochte dominates 400m IM, Phelps fourth. China power to two swimming golds, lead medals table. Cyclist Vinokourov trumps home hope Cavendish in road race.
Phelps, unthinkably, finished without a medal in the 400 metres individual medley -- a fate shared in the men's road race by British favourite and world champion Mark Cavendish, outmanoeuvred 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 metres 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.
New Zealand's men took the opening day of the Olympic rowing regatta by storm, setting one world best time, breaking an Olympic record and generally looking untouchable.
Eric Murray and Hamish Bond maintained their incredible recent form to win their pair heat on Dorney Lake by some nine seconds, or three boat lengths of clear water, to shatter the old world best time and storm into the semi-final.
The pair, who won gold in the last three world championships and have not been beaten since they teamed up in 2009, recorded a time over 2,000 metres of six minutes and eight seconds, well below the previous world best time of 6:14 set by Britain's Matthew Pinsent and James Cracknell in Seville 10 years ago.
The time, recorded on a hot day with a slight tail wind, also smashed the previous Olympic best time of 6:20 which was set by Pinsent and Steve Redgrave in Atlanta in 1996.
Mark Cavendish 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.
Switzerland's Olympic time trial champion Fabian Cancellara who was in the breakaway group crashed out with about 15 km to go in the race,
leaving him with a bloodied arm and ruining his chances of claiming a medal.
He will make a decision in the next days about appearing in the time trial.
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.
"Second in Sydney, 12 years later, gold, unbelievable, yeah," he said.
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.
At Wimbledon, Serena Williams breezed past Serbia's Jelena Jankovic, with U.S. first lady Michelle Obama cheering her on.
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 medallist Valentina Vezzali.
Italian women swept the Olympic medals in foil on Saturday but crowned a new queen in Elisa Di Francisca who clawed her way back in the waning seconds of regulation to land the final touch in sudden death overtime against team mate Arianna Errigo.
Valentina Vezzali, Italy's reigning world champion, muscled past South Korea's Nam Hyun-hee to win bronze at London's ExCeL Centre.
In an amazing display of discipline and focus she snatched the 13-12 victory from a seemingly insurmountable deficit that had the world's greatest female foilist seconds from defeat, down by four points only to come back and win.
It was some consolation for Vezzali, who had been chasing her fourth consecutive individual Olympic gold medal after carrying the flag for her nation into London's Olympic Stadium the night before.
The 38-year-old has now won 29 Olympic and world championship medals and has her sights on the record of 39 set by countryman Edoardo Mangiarotti, who died in May aged 93. He won 13 Olympic medals between 1936-60.
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 metres 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 metres 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 favourite 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 favourite 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 medallist 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 metres freestyle relay, ahead of the Netherlands and the United States.
Earlier 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.
Albanian weightlifter Hysen Pulaku became the first to be ejected from the London Games after testing positive for an anabolic steroid.