Kenya's David Rudisha stormed to 800 metres gold in a world record time at the London Olympics on Thursday to cap four years of dominance in the two-lap event with a brilliant run.

With the 80,000 crowd in the Olympic Stadium roaring him on, the world champion scorched around the Olympic Stadium in one minute 40.91 to beat the mark of 1.41.01 he set two years ago in Italy.

"I had no doubt about winning but I was waiting for perfect conditions to break the record," the 23-year-old told reporters.

"I am happy. I've waited for this moment for a long time. To come here and get a world record is unbelievable."

Nijel Amos of Botswana won silver in 1.41.73 to claim his country's first Olympic medal and bronze went to Timothy Kitum of Kenya in 1.42.53.

All but one of the eight athletes in the field ran personal bests and the time run by Britain's Andrew Osagie, who was last to cross the line, would have been good enough for gold at the last three Games.

"Those kind of times would get a medal in any other championships, but David is on such good form," Osagie said. "It was an honour to be in that race."

The last runner in the field to set himself for the start, Rudisha hit the front halfway through the back straight and after that, with his smooth loping stride eating up the track, it was a straight run against the clock.

He pushed again after taking the bell in 49.28 seconds and came into the home straight 10 metres clear of teenager Amos, finding just enough in the tank to take him over the line a tenth of a second inside his own record.

Dubbed the "Pride of Africa" after winning the world junior title in 2006, Rudisha missed the Beijing Olympics through injury and was boxed in during the semi-finals at the 2009 world championships.

The following year, though, he shattered Wilson Kipketer's 13-year-old world record, only to improve it again the following week as he went unbeaten for 34 meets until the end of last season.

As well as winning him the world athlete of the year award, he was also made a warrior by his Maasai tribe, an honour that would once have required the killing of a lion among the semi-nomadic people.

Rudisha followed his father Daniel, who won a silver in the 4x400m relay in Mexico in 1968, as a Games medallist but is the first Olympic champion from his Maasai tribe.

His hopes of emulating his father by running the one-lap relay in London were dashed when Kenya were disqualified from the heats earlier on Thursday.

Neither Kipketer, who ran for Denmark, nor his predecessor as 800m world record holder, Briton Sebastian Coe, won Olympic gold in the event.

"Lord Coe is a good friend of mine," Rudisha said. "I came here in February and he showed me around the stadium. I wanted to come here and make him proud."

Coe is now chairman of the London organising committee for the Games and hailed Rudisha's feat as "one of the great Olympic victories".

"That was simply an unbelievable performance," he said. "David Rudisha showed supreme physical and mental confidence to run like that in an Olympic final. Instead of just doing enough to win the race he wanted to do something extraordinary.

"I feel privileged to have witnessed it in London."