So, where did it all go wrong, Mark?

So whatever did happen to that likely lad, the sprinter with the double-barrelled name and the shotgun blast of speed? Mark Lewis-Francis is sitting in a corner of Costa Coffee at Heathrow Airport, sipping his skinny latte and patiently working his way through questions about his unfulfilled talent, about how eight years have passed since the one and only occasion on which he broke 10 seconds for the 100 metres, about being dropped from Lottery funding, and about missing the Beijing Olympics because of an Achilles tendon operation. All the while, it transpires, he has the ultimate prize in sport tucked away in the backpack propped up against his chair leg.

He has had it with him to show to a group of schoolchildren at a Spar Sprints Masterclass at Ballyclare in Northern Ireland. Suddenly, you feel like the porter who brought George Best his bottle of vintage champagne while Northern Ireland's finest was sitting on a hotel bed with a naked Miss World (Mary Stavin) and with the winnings from a casino flutter strewn across the duvet. So, Mr Lewis-Francis, with your skinny latte and your big fat Olympic gold medal, where did it all go wrong?

It is a question that Paula Radcliffe, Colin Jackson, Steve Cram, Ron Clarke and Jim Ryun would dearly love to be asked of them. World record-breakers and all-time athletics legends all, but not one Olympic gold medal between them. Unlike the man who anchored the Great Britain 4 x 100m relay team to their sensational upset victory against the United States in Athens in 2004.

"Yeah, and that's what keeps me going, my Olympic gold medal," Lewis-Francis says, reflecting back through the lean years to the spine-tingling night he brought home the bacon – or, rather, the baton – ahead of the fast-finishing Maurice Greene. "Showing it to the kids today, seeing the look on their faces when they were touching it, was inspiring to me. I have achieved it, they can achieve it. And no one can take it away from me.

"All the negative stuff people have said about me, it fuels my fire. It makes me get up in the morning and train harder. I have had it for the last four years, but I finished ninth at the last World Championships, in Osaka in 2007 [he missed the eight-strong final by 0.01sec]. I have been out injured for a year, but if I can get back and build on that, I can't complain.

"I take the Olympic gold medal for granted sometimes. I lock it away and forget about it. When I took it out this morning it made me appreciate what I've done in my career so far. And there's more to come. I'm 26. I'm not that old. I've still got 2012 and maybe one more Olympics after that."

It is good to see the one-time Billy Whizz Kid, the super-fast boy from West Bromwich, on such fine form. Olympic relay gold medal apart, Lewis-Francis has had a tough time of it since his days as a teenage sensation, when he clocked 9.97sec for 100m at the World Championships in Edmonton in 2001 (a malfunctioning wind-gauge rendered the time technically "unofficial") and 10.04sec at a 2002 Golden League meeting in Paris.

He has had "every injury under the sun", that Achilles tendon problem wiping out his entire 2008 season. He has tested positive for cannabis (for which he was given a warning in 2005). He has lost his Lottery funding and had to start eating into his savings to continue as a full-time athlete. He has also endured "the trials and tribulations" of moving to the south and changing coaches, not once but twice.

Now, though, having recovered from an Achilles operation, he has settled into life as a resident of Slough, the home of the Mars Bar, and as a member of Linford Christie's training group at Brunel University in Uxbridge. "Linford's a guy who's been there and done it," he says. "The speedwork part of the training we do is very technical, and that's what I need to get to the next level.

"I'm not saying I'm going to go out there and run world-record times. I've had a major operation. I've got to get back my international status, then look to make finals again. Once you make finals, anything can happen, but I've got to get there first. I believe I can.

"I don't believe talent goes away. I believe that you have to work a little bit harder to get it back. And I've been doing that. I'm not the kind of guy who's out to prove people wrong. But, coming back now, I am hungrier than ever. I'm more determined. The last year was so hard – especially watching the Olympics."

Still, following the Beijing Games from afar did have its compensations for Lewis-Francis: seeing another former teenage sprint sensation fulfil his youthful potential with a triple gold medal-winning, triple world record-breaking vengeance. "That made me sit up, wipe away the tears and refocus," he says of Usain Bolt. "It made me get down the track and do my rehab. This guy had been to all the major champs, reached many of the finals, but never achieved what he did in Beijing. That just made me believe that anything is possible."

There are parallels between the Lightning Bolt and the double-barrelled Briton. Both won world junior sprint titles and were hailed as future world-beaters while they were still in their teens. Both have benefited from the long-term faith and guidance of Ricky Simms, the manager they happen to share. They have also trained together in Jamaica and will be next to each other on the start line in the Great City Games 150m street race in Manchester on 17 May.

For Bolt, racing in Britain for the first time since his Beijing exploits, it is likely to be something of a Coronation Street affair. For Lewis-Francis, five years down the line from his crowning Olympic moment, it will be a step down the comeback road.

Since 2004, SPAR Sprints initiative has been committed to supporting young sprinters of all abilities across the UK by offering support through experienced coaches and athletes