The first approach came when Darren Campbell was 20 or 21, he's not sure which, although in every other respect the memory – of being encouraged to take performance-enhancing drugs – remains vivid. The suggestion came from one of the medical team treating him after a car accident, a man who waited until they had established a rapport, and then made his move.
"He went, 'you need to do what the others are doing, get on the juice'," Campbell recalls. "I went 'the juice?' He went, 'yeah, the juice'. I went 'right, OK' and that's one of the reasons I retired." Dismayed by the evidence of widespread cheating in athletics, Campbell turned his back on the sport for two years, got a job with an insurance company and played semi-professional football. But a couple of years later, watching Toby Box and Jason John finishing second and third behind Linford Christie at a televised meeting in Sheffield, he felt the urge to race again. "I thought 'I need to go back, I used to beat those guys'."
He asked Christie if they could train together, but at first was turned down. Christie didn't think he was serious enough about athletics, yet Campbell turned out to be sufficiently serious to make the 1996 Olympic squad, and in Sydney four years later, to win the 200m silver medal. Then came the second invitation to cheat. "I was training in America, and a chiropractor I was seeing said to me, 'look, there's this new thing out. What they do, they inject out of the embryo of an unborn baby'. In my head I thought, 'that sounds like growth hormones'. I went 'OK, I'll let you know'. I never went back."
I ask why he wasn't more forceful, why he didn't go straight to the authorities or at least lambast the pair for trying to corrupt him? "Yeah, but unless it's recorded, it's just my word against theirs, and who would believe this black kid from Moss Side, who'd been surrounded by drugs most of his life? Why would I say no?"
Why did he say no? "Because my mum had told me that the day I felt I needed drugs to be successful, was the day I should stop. I only fear my mum and God, so that was enough. When you grow up in a council flat watching your mum do three jobs to feed and clothe you, when you listen to her crying at night because of the stress, and then you find yourself earning a good living, in a legal way, you know you're more blessed than you were at the beginning."
It is five years since Campbell retired from athletics – with an Olympic gold medal in the 4x100m relay, in 2004, the most glittering of the many prizes he accumulated – and sport continues to provide him with a good living. We meet in his office at a retail park in the heart of the Welsh Valleys, from where he runs his thriving sports nutrition company, Pro Athlete Supplementation. Currently, PAS look after the nutrition needs of 12 Premier League football clubs and 15 Championship clubs. Rugby union outfits Cardiff Blues, Llanelli Scarlets, Harlequins and Biarritz are also on the books. So is the WBO light-heavyweight champion Nathan Cleverly, who trains just down the road.
Campbell's business partner, the man who conceived the whole enterprise, is Jon Williams, nutritionist to the Welsh rugby team. They stock more than 20 products, protein drinks and the like, and they make the stuff themselves, to be sure that there's no chance of cross-contamination, nothing that might fall foul of the stringent testing procedures. It can't hurt business that Campbell waved the anti-doping banner as energetically as he did during his running career, notably at the 2006 European Championships in Gothenburg, when after winning the relay he declined to join the lap of honour as a protest against his team-mate Dwain Chambers, who had served a two-year ban for taking steroids. As soon as I mention Chambers, a nice young man from the marketing agency Fast Track, who has travelled all the way from London to sit in on our interview, and has plainly been waiting for this very moment, interjects to say that he doesn't want anything "too controversial coming out of this". It seems that the very name of Chambers, who remains determined to overturn his lifetime Olympic ban, still causes anxiety in athletics circles. Especially in tandem with that of Campbell, but the charismatic 38-year-old Mancunian laughs at the notion of being muzzled. He has never shied from controversy, and he's not about to start now.
"Listen, with Dwain ... people say I didn't like him, but it wasn't that. I wanted him to help the fight [against drugs], to right the wrong, and he didn't. Nobody ever properly asked me why I didn't do the lap of honour. I'd already told the team manager that I wasn't comfortable running in the relay team with Dwain, that if he was going to be in the team I'd be happy to stay at home. He said, 'look, Dwain will only run in an emergency'. Well, we hadn't won a gold medal in those championships; that was considered an emergency. But it didn't feel right to do the lap of honour."
Chambers has since apologised for his transgressions, and Campbell assures me that, on the rare occasions they see each other, they get on OK. Indeed, with the American athlete LaShawn Merritt having had a ban rescinded on appeal, he thinks the same indulgence should be extended to Chambers. "But my feelings [about drug-taking] have always been the same," he adds. "At what point does the sport decide enough is enough? People are still saying, 'should it be a life ban, should it be two years?' For me, it's got to be life. You can't rob the sport, then come back to the sport, that don't make sense. It's like working in a bank, and putting money in your pocket every so often. Could you serve a suspension, then go back and work in the bank? Course not."
His conviction is fuelled by a lingering sense of injustice. Campbell would have at least one more gold medal in his locker if it hadn't been for other people cheating. He had to hand back the relay gold he won at the 2002 European Championships, because Chambers was part of the team. Moreover, the man who beat him in the Olympic 200m final in Sydney was Konstantinos Kenteris, the Greek sprinter who was forced to withdraw in Athens four years later because of a doping violation.
"I let other people debate that one," Campbell says. "But I'll never forget the night, going to the drugs room afterwards and Ato Bolden saying to me, 'don't worry, by tomorrow morning that'll be gold'." His silver medal never was upgraded, but in the 2004 Games came that unforgettable performance in the relay, which he still uses as a stick, or perhaps a baton, to beat his former critics.
"Michael Johnson and Colin Jackson had slated me [earlier in the competition]. They said I was faking injury, so [team doctor] Bryan English went on TV and showed my scans. It was all nonsense. I was even working with Dr Muller-Wohlfahrt, the Bayern Munich doctor, which them two fools did not realise. But I had a war of words with Michael Johnson, and after that I said to the other guys, 'look, I'm ready to go home. If you want me to stay, I'll stay, because I'm a team player, and growing up in gangs you know you can't just leave people. But I'm willing to go home'. They said they wanted me to stay, and I knew then we'd win."
It was a close-run thing, the narrowest of victories over the highly-fancied Americans in what is still, even on YouTube, an exhilarating spectacle. "People ask me if I'd rather have an individual gold medal," he says, "but actually I'd rather have it as part of a team, maybe because I play team sports. Now, when I see Mark [Lewis-Francis], Marlon [Devonish], Jason [Gardener], we have a special bond. We did something ... ridiculous. And I feel blessed to have got what my career deserved."
His career now is about helping others to realise their potential, not only with the nutrition products but with a busy sideline in speed coaching that started when someone at Chelsea, who were already PAS customers, asked if he might be able to help Andrei Shevchenko find an extra yard of pace.
"Initially I wasn't allowed at the training ground. I don't think Mourinho wanted anyone to help Shevchenko. So I started helping him on his tennis court, and he started to improve. Then Andy Johnson phoned me up, while he was at Everton. It progressed from there. Mark Cueto gave me a call, and off the back of working with him I got Richard Wigglesworth. Cuets brought him down, but when I first saw him run, I was like 'oh my God, I can't help him'. His co-ordination, his rhythm, were horrible. I didn't know where to start. But we increased his pace and he got into the England team. I also try to pass on a positive mental attitude. Lewis Moody said that's part of how I help them, because I think anything's possible."
He has been empowered by positive thought, he says, since childhood. "All I had was belief, instilled by my mother. But when I played in the same soccer school of excellence as Ryan Giggs, and saw what he could do with a football at pace, and what I could do, I started thinking that maybe I was only good at sports like football and basketball because I was fast, and maybe I should stick to a sport where it was about being fast."
There is, however, such a thing as being too fast. "If I worked with Theo Walcott I'd tell him to slow down. He's so quick that he can afford to take more time. If you're looking for perfection in football it's Thierry Henry. At pace he was so relaxed, and that's what Walcott needs to learn."
The other footballer he often cites as an example, not of how to run but how not to, is Michael Owen. "He kept pulling his hamstrings, because there's not much of a knee lift. That's why Andy Johnson came to me, and Cuets, so I could change the biomechanics of how they run. If you're pulling your hamstring in the 30th minute it's not because you're not warmed up, it's because of your technique. That's what I change. A lot of those guys are quick, but they've never been taught how to run."
I venture that Charles van Commenee, the head honcho at UK Athletics, could do worse than recruit Campbell ahead of 2012. He laughs. "I like Charles. He's been a breath of fresh air. He's tough with them, and I love that, though I think he needs to be softer with some, like Jenny Meadows. But no, I'm too opinionated for them. I think lottery funding is a fantastic idea, but if you give young athletes 30k, 40k a year, they can lose that hunger. The problem is not funding, it's making sure it's used in the right way."
And what does Mr Positive Thinking think of our Olympic medal hopes? For once, positivity fails him. "I was looking for a lot more of our athletes to make finals in [the world championships] South Korea," he says. "And of the small group who won medals, some will get injured, which lessens our chances again. You can't underestimate the competition, either. I've always felt Dai Greene was a real class act, and that he would win in London." Darren Campbell stretches out two long, tracksuited legs. "But the problem now is that he's the hunted one, so the game changes," says the man still at the top of his own game.
Darren Campbell is supporting the 'Be There with Team 2012' appeal, which is raising funds for the 1,200 athletes in Team 2012, presented by Visa. To be in with a chance of winning tickets to London 2012, donate to the appeal at www.team-2012.com