All eyes on Bolt-Blake duel

For the first time since the advent of electronic timing, the field for the blue riband event of the Games will comprise the four fastest men in history - champion Usain Bolt, Yohan Blake, Asafa Powell and Tyson Gay.

Bolt rewrote the record books at the 2008 Beijing Games with a dazzling sprint double that turned logic on its head and forced a recalibration of what had previously been thought humanly possible.

The good news for the London organisers is that the cheerful 25-year-old is back, professing his readiness to mount a successful defence of his 100m and 200m titles from four years ago in his bid to "become a legend".

"I am the Olympic champion and I have to show the world I am the best," Bolt said on the eve of the Games.

The even better news is that he will have a titanic battle on his hands, the first chinks in his armour revealed when he was beaten in both the 100 and 200m in the Jamaican Olympic trials by training partner Blake.

Blake, crowned world champion in Daegu last year after Bolt sensationally false started in the final, is a serious gold medal contender.

"My philosophy is that the sky's the limit," Blake said. "I've always wanted to be at the Olympics. I've got no message for Usain Bolt. He's a good guy. I'm not focusing on Usain."

Other rivals in the 100m will likely be another Jamaican, Powell, and the Americans Gay and Justin Gatlin.

Gatlin won the 100m title in Athens in 2004 but was barred from defending his title in Beijing after he was banned for doping offences.

Gay, who has committed to racing just the 100m in London, has made a slow start to the season, but came through the US trials alongside Gatlin, and said he was ready for the challenge after an injury-plagued period.

"It's a lot of pressure; I'm not going to lie. The missing piece in my heart is an Olympic medal," said Gay, who will turn 30 four days after the 100m final on Sunday.

Track and field will run from Friday through until August 12, the last 10 days of the Games, at the newly-built Olympic Stadium, with an estimated 2 000 athletes competing in 47 events.