Olympic 100 metres champion Maurice Greene was defeated for the second time in eight days at the London Grand Prix on Friday in a potentially significant victory for Jamaican Asafa Powell.

Powell equalled the Jamaican record of 9.91 seconds he set in June against a field worthy of next month's Athens Olympic final.

Greene, who also finished second at the Paris Golden League meeting last Friday at the start of his pre-Games European campaign, clocked 9.97 to take second place.

Russian Yelena Isinbayeva set her second world women's pole vault in the space of a week when she cleared 4.90 metres. Isinbayeva vaulted 4.89 in Birmingham last Sunday and has now set three world records on British soil this year.

Her compatriot and great rival Svetlana Feofanova failed with two ambitious attempts to extend the record to 4.95.

Powell maintained his unbeaten record over the 100 this year despite getting out of the blocks marginally slower than Greene, who won the U.S. title this month and appears to be back to his best after two years of fluctuating form following a succession of injuries including a broken leg.

"That gave me a lot of confidence," said Powell, who was disqualified in the quarter-finals at the Paris world championships last August for false start.

"He was Olympic champion last time but I hope to beat him this year as I have beaten him today. I can cope with all of the hype and expectation."

GREAT RACE

Greene said Powell had run a great race.

"I was not surprised he won tonight, my start was not the best," he said. "I was moving side to side when I came out of the blocks but I will fix that for my next race."

Kim Collins of St Kitts and Nevis, who won the world title in Paris last year after three-times champion Greene was injured in the semi-finals, finished fifth in 10.14.

"There was a lot of pressure because it was the first time I have faced Maurice Greene this year," he said. "Everybody has been waiting for it."

Not one of Britain's Olympic hopes even qualified for the final. World bronze medallist Darren Campbell, their brightest hope for Athens after European champion Dwain Chambers was banned for two years after a positive test for THG (tetrahydrogestrinone), finished sixth in the first heat.

Former world junior champion Mark Lewis-Francis did even worse, finishing eighth and last, while in the second heat world indoor 60 metres gold medallist Jason Gardener came eighth with the other Briton Christian Malcolm fifth.

There was better news for Britain in the 400 metres hurdles where Commonwealth gold medallist Chris Rawlinson defeated the American champion James Carter.

Carter looked smooth and controlled until the final barrier when Rawlinson's strength allowed him to pull slowly but inexorably ahead.

Rawlinson clocked 48.48 seconds with Carter, the fastest man in the world this year, 0.15 of a second behind.

Twice Olympic silver medallist Steve Backley finished second in his final competition at Crystal Palace to Norway's Andreas Thorkildsen.

Backley, 35, who will retire after Athens set a world record at the London meeting in 1990.

"I felt as though there was a bigger throw in me," said Backley, who went past 80 metres with all six throws with a best of 83.42. Thorkildsen threw 84.45 metres.

Twice Olympic 10,000 metres champion Haile Gebrselassie, who will move up to the marathon permanently after Athens, also said farewell to Crystal Palace with victory in the 5,000 metres.

The little Ethiopian was forced to work hard for his win, running down Australian Craig Mottram in the straight for victory in 12 minutes 55.51 seconds.

"I was surprised at the end," said Gebrselassie. "I didn't expect him, he was fantastic."