I will prove you can win the Tour without using drugs

"It's is the hardest sporting event in the world, and in cycling it's bigger than anything else, the Olympics, the world championships, whatever," he says, struggling to convey the magnitude.

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"It's huge. World championships and Olympics you can dream of with your feet on the ground. The Tour is more of dream with your head in the clouds. To be able to do it is unbelievable."

For the 22-year-old Briton, Saturday's prologue stage will be even more special, given that it will be in London, taking in Trafalgar Square and Big Ben before a grandstand finish on The Mall.

"It will never happen again in my lifetime, so to be able to ride in London is perfect. Just to ride in the Tour is brilliant. Everything about it will be amazing to see. Everyone has told me stories but I still can't picture it."

Cavendish, from the Isle of Man, is one of the young stars of the pro-cycling world, a sprinter who, in his first professional season with T-Mobile, has made a remarkable breakthrough, winning stages at prestigious races such as the Tour of Catalunya and Four Days of Dunkirk.

But there is more to Cavendish's dream than just riding in the world's greatest race. He wants to do it clean. Saturday's crowds lining the London streets will be caught in the Tour's eternal dilemma: do you marvel at the spectacle or scowl at the cynicism that pollutes the sport?

Of recent Tour de France winners, Bjarne Riis (1996) confessed in May to taking EPO throughout his career, while Jan Ullrich (1997) was sacked by his team and quit the sport last year shortly before he was proven to be linked to the latest doping scandal.

Marco Pantani (1998) raced with a red-blood count considered to be well above normal and later died of a cocaine overdose. Floyd Landis (2006) failed a test for testosterone, a result he is still fighting in an arbitration hearing.

Yet Cavendish believes he is part of the answer to the roll call of shame.

"Cycling is a beautiful sport but its name has been dragged through the dirt in the last few years. That is nothing to do with me, I wasn't in professional cycling. All I want now is for everyone to push forward to show what a beautiful sport it is.

"I want my career to last 15 years without people pointing the finger because you're a professional cyclist. It just takes one generation to stop it, to say: 'Enough is enough'.

"You could get completely rid of it. And, hopefully, that is what's happening right now. I've come from a generation in which it's cool to be clean."

He knows to be wary. The last bright young Briton who took the Tour by storm was David Millar, donning the yellow jersey in 2000 and ending the Tour with the prestigious white jersey for the best young rider. He turned to EPO in 2001, was arrested in 2004 and served a two-year ban.

He rides this year as team leader for Saunier Duval-Prodir, now a reformed evangelist for anti-doping. "The Tour is a beautiful event but it has been undermined," said Millar recently. "It is tragic what has happened — it has got to be sorted out. Why did I dope? I came to the conclusion, why did I not dope?"

But Cavendish retains his idealism: "Doping is f****** dangerous. These things happen in all aspects of life. You're always going to get d***heads in every area of life, but I think I proved this year it's not needed. I think you can win clean. I love this sport and I make sacrifices for it. All I want to do is ride my bike. I really can't be bothered to be doing what other people do. It just doesn't appeal to me."

Cavendish will not finish the Tour this year. He is racing to gain experience. But in the future he can aspire to winning the prestigious green jersey for sprint specialists. BUT he is already something of a poster boy for the sport. Mired in the controversy of endless doping scandals, the latest being last year's Spanish judicial inquiry, Operation Puerto, which uncovered systematic doping throughout the sport, the likes of Cavendish are touted as a new breed.

The disgrace of Puerto, the confessions of Riis and Landis's positive test has led Enrico Carpani, the spokesman for the sport's governing body, the UCI, to speak of 2007 as Year Zero for the sport.

"This is a new beginning," he says. "We would like to help build a new generation of cyclists who can show that you can win without doping. It's beautiful when someone like Mark comes along when he says he wants to be the representative of that new generation.

"He's a young guy who says he doesn't want to be merged with the past of the sport. It is maybe a bit too strong and too direct for people in the traditional cycling countries of Italy or France. But in the past the subject was taboo. Nobody spoke about it."

The UCI are attempting to do their bit. Along with increased out-ofcompetition tests and blood-testing, last month they introduced a pledge for cyclists to sign.

In it, competitors declare themselves opposed to doping, promising to pay a year's salary if they are convicted of doping offences and commit to providing DNA samples to help the Puerto investigation.

Carpani admits they cannot sanction cyclists if they refuse to sign, leading some to suggest it is a mere public relations exercise.

"But our aim was to give the opportunity to cyclists to take a stance," he adds. "Everybody is under suspicion and we wanted to give cyclists an opportunity to say: 'I have nothing do with that'." Should we then conclude that those who have refused to sign are doping? "I won't say that we intended that," says Carpani. "But if you do draw this conclusion, it's natural."

Cavendish and the entire T-Mobile team have signed, along with almost 200 others. It will be intriguing to see how many more put pen to paper before the Tour starts next Saturday.

Astana, the team who contain Tour favourite, Kazakhstan's Alexander Vinokourov, and who were born out of the discredited Liberty-Seguros team, are listed as a team in which none of the members have signed.

Team spokesperson Corinne Druey insists this is a misrepresentation. "All of our riders have signed the declaration or are in the process of signing it," she says. "Of course, they will all have signed it by the time the Tour begins."

Despite these admirable efforts, even Carpani cannot guarantee a clean Tour. "It's impossible for me to say:'Yes, you will be able to believe in the next winner of the Tour de France'. But what cycling can do is make it very, very difficult if you want to race at this level and dope."