Dwain Chambers has been Britain's highest-profile sprinter ever since he took World Championship bronze in 1999 at the age of 22.

He showed enormous promise as a youngster, winning 100m and sprint relay gold in the 1995 European Juniors and setting a new world junior record when repeating the feat in 1997.

But Chambers has struggled to fulfil his enormous potential at the highest level.

At the 2003 Worlds, he settled into his blocks as favourite but came home fourth in a time well outside his personal best.

It was the same story at the 2002 Commonwealth Games, where he limped off the track with cramp mid-race.

His greatest moment on the track came when he blazed to European gold in Munich last summer, a performance which it was hoped would give him the self-belief to go on to become the world number one.

With the decline in form of Olympic champion Maurice Greene, there was a gap at the top of world sprinting.

But it was Tim Montgomery, and not Chambers, who broke Greene's 100m world record.

The fact that Chambers equalled Linford Christie's British and European record of 9.87secs behind Montgomery was little consolation to the Londoner.

At the Worlds, Chambers was beaten by Kim Collins, the same man who had beaten him to Commonwealth gold, as well as his British team-mate Darren Campbell.

Campbell - a sprinter much slower than Chambers on paper- has developed the knack of performing above his best at the major championships, something Chambers has yet to learn.

In a bid to change his fortunes, Chambers left his long-term coach Mike McFarlane a year ago to link up full time with 73-year-old Remi Korchemny, the Ukrainian who coached Valery Borzov to Olympic 100m and 200m gold in 1972.

Chambers was convinced that Korchemny had the technical expertise he needed to make him the best in the world.

So confident was the Briton, he began last season claiming that he was in the sort of shape to run 9.65secs - a time which would have obliterated the world record.

But the season began badly with two defeats to his younger British rival Mark Lewis-Francis.

Chambers' form picked up at the London Grand Prix in August, when he beat the cream of the world's talent.

But by then he had already given the drugs test that was to subsequently test positive for THG.