Bradley Wiggins became the first man to win the Tour de France and Olympic gold in the same year with an imperious victory in the London 2012 time-trial.

The 32-year-old claimed his fourth Olympic gold and seventh medal in all, surpassing Steve Redgrave with a British record haul of Games medals.

Wiggins was the penultimate of 37 riders to take to the course and completed the 44-kilometre route in 50 minutes 39 seconds to triumph by 42 seconds, with fellow Briton Chris Froome third in 51mins 47secs.

World champion Tony Martin of Germany clocked 51:21 to claim silver.

Ireland's David McCann finished 27th overall in a time of 56:03.

Wiggins won the Tour's two long time-trials last month and was optimistic of success after three Olympic gold medals on the track and six in all in his previous three Games.

The Londoner showed no signs of fatigue following Saturday's road race and reached the first time check after 7.3km, in 8:27, five seconds behind Martin, but thereafter forged forward and took the lead at the second time check, after 18.4km.

Wiggins was 11 seconds faster than the German, going through in 23:14 and enhanced his advantage at the third on course time check, after 29.9km and with 14.1km remaining.

The Briton was 22 seconds quicker than Martin, going through in 34:43, compared to the German's 35:06.

Froome was third fastest in 35:25, with Cancellara fifth fastest.

Froome finished second to Wiggins in each of the Tour's two long time-trials in claiming second spot in Paris overall and replicated those performances, finishing strongly to set the provisional best before Martin and then Wiggins beat him.

Wiggins accepted the acclaim of the crowd and a warm embrace from Martin after achieving the second of his two main goals for 2012.

It is the first time Britain's men have won gold on the road during the Olympics and the first medals since Atlanta in 1996 when Chris Boardman won time-trial bronze and Max Sciandri was third in the road race.

Earlier in thye day, American Kristin Armstrong retained her Olympic time trial title with an impressive display of power and poise.

Armstrong, the Beijing champion, averaged over 46 kph over the 29-kilometre course to beat world champion Judith Arndt of Germany, who took silver 15 seconds behind, according to provisional results.

Russian Olga Zabelinskaya, the road race bronze medallist, claimed bronze again, 22 seconds off the pace.

On a course setting off and finishing at the opulent Hampton Court Palace, built by King Henry VIII on the banks of the Thames on the outskirts of London, Armstrong made the best start.

She clocked the fastest time at the first check point after 9.1 kilometres on Burwood road ahead of New Zealand's Linda Melanie Villumsen and Canadian Clara Hughes.

Arndt made a strong impression as she powered past road race Olympic champion Marianne Vos of the Netherlands, who left the start house 1:30 earlier, before the halfway point.

At the second check point after 20.1 km, Arndt was third, eight seconds off Armstrong's pace.