It will all be over in a matter of seconds and Dwain Chambers, sporting pariah or witch-hunt victim depending on your view, knows that the comeback could also be the farewell. Even a gold medal in the 60 metres at the World Indoor Championships this evening might not save him from being thrown on to the scrapheap.

Chambers, banned for two years in 2004 for testing positive for tetrahydrogestrinone (THG), looked almost dumbfounded by the furore his presence in Valencia has caused. He came back two years ago to minimal fuss, but the parameters have changed, promoters have closed ranks and managers have signed up to an agreement not to work with drug cheats. It means that, after tonight, Chambers may have nowhere left to run other than into a High Court battle against his British Olympic Association life ban.

“I’ll be back,” he insisted as he strolled through the lobby of the Great Britain team hotel. “There will always be a way back, some way, somehow. I’m optimistic that my performance here might change things.

“I don’t know why it has escalated the way it has, but it’s brought more attention to me and to the sport, good, bad or ugly. What I’d like is to bring attention in a positive way because what I did then was me in the past. I’ve taken a positive stance and want to show there is life after mistakes.”

He may not be afforded the chance to build bridges. Dave Collins, the UK Athletics (UKA) performance director, conceded that it would be “remarkable” if he won gold this evening, but he headed the panel that picked Chambers and then said it wished it had not.

The odds are also against him, although Leonard Scott, the champion, is absent with injury and Asafa Powell and Tyson Gay, the world’s top outdoor sprinters, are not troubling themselves with indoor matters in Olympic year. In their place, Olusoji Fasuba, of Nigeria, is the fastest man this year.

Chambers reiterated his desire to help to clean up the sport and said he would gladly meet Dame Tanni Grey-Thompson, who is leading UKA’s anti-doping review. “We don’t want another me,” he said. “ This is an important time coming up to 2012 and we have to make sure the medals are British and not from other countries.”

Those who feel that Chambers has been singled out will note that the champ-ionships open today with the shot, in which Carl Myerscough, another convicted drugs cheat, competes for Britain. To suggest the cases are different merely because Myerscough has remained committed to the sport is a flimsy dividing line.

Kelly Sotherton is in action this morning against a woman with a drugs conviction. Lyudmila Blonska pipped the Briton to silver at the World Championships last August and Sotherton will be hoping to take advantage of Carolina Klüft’s absence to win gold in the pentathlon.

Also hoping to qualify today in the long jump is Chris Tomlinson, who has been told by his fiancée not to bother coming home if he fails to win a medal. “She’s fed up with all the promise and potential,” Tomlinson said.

He is phlegmatic about any success being overshadowed by the Chambers story. “That’s life,” he said. “I could win Olympic gold and break the world record and it would not make the back page if Cristiano Ronaldo had a fight with Wayne Rooney.”

It is Chambers’s return and perhaps his final bow that will dominate the day. He says that his team-mates have been fine and his head is all right. “I just want to go out, have fun and run like a bat out of hell,” he said.

D-Day for Dwain

11.45am 60 metres first round
4.30pm 60 metres semi-final
7.45pm 60 metres final

The rivals

Olusoji Fasuba, of Nigeria, is the fastest man this year with 6.51sec, but Michael Rodgers, from the US (6.54), and Kim Collins, the 2003 world champion (6.56), will also be in the fray. Also watch out for Simeon Williamson, the second Briton, who has run 6.57 this year. Chambers is the joint fifth quickest in 2008 with 6.56.