Mark Cavendish demonstrated once again that he is the fastest sprinter in world cycling with a record-breaking third stage win in the Tour de France in Narbonne yesterday.

The 23-year-old's victory in the 168-kilometre twelfth stage made him the first Briton to win three stages of the Tour and vindicated his decision to carry on racing after a bad crash consigned him to last place on the summit finish to Hautacam.

“This was the hardest of all three sprints,” Cavendish said. “It was windy and the pace was really fast, but a win is a win. I'm glad I could get over the Pyrenees for my [Columbia] team-mates. You've seen how hard they've worked in the last few weeks and you saw how hard they worked today. It's just so nice to get another one.

“I have had a few problems with injuries, but that's the Tour. Anything can happen. You've got to take the pleasure with the pain.

“It was a little bit harder than the other sprints because it was a headwind and it had been windy all day. I'm also a little tired, but I was still the fastest across the line. Instead of winning by a few bike lengths, I only won by a bike length this time, so it shows how tired I am.”

Only the achievements of Barry Hoban, who took double stage wins in the 1969 and 1973 Tours, compare to the Isle of Man rider's success. “It makes me very proud to be the first British rider to win three stages in a major tour,” Cavendish said. “It's nice that I won them in very different weather conditions, too, that makes it more special. That also shows just how good my team are at handling all sorts of sprints and all sorts of situations. I got dropped off on the perfect wheel.”

Cavendish's win, which he celebrated by raising three fingers to signify his hat-trick as he crossed the line, lifted the Tour out of the doldrums after Riccardo Ricco, the double stage-winner, tested positive for erythropoietin (EPO). The Italian rider was detained by French police at yesterday's stage start in Lavelanet and his team, Saunier Duval, withdrew from the race.

“I think it's a good thing,” Cavendish said. “I believe that changes are happening. Obviously it's a cloud over what's been a pretty decent Tour de France, but every time someone gets caught it's somebody else who's not getting away with it.”

However, it seems certain that Ricco will not be the last rider to fall foul of the new testing regime. The AFLD, the French anti-doping agency that is conducting controls at this year's Tour, is showing a zeal that was never present when the International Cycling Union was supervising the Tour's drug tests.

Unsatisfactorily, though, even the AFLD is playing catch-up. To date, the outcome of the first four days of testing has been made public. The results from the first mountain stages, in which a product as effective as EPO comes into its own, have yet to be released.

Competing in only his second Tour, Ricco should have been the spear-carrier for a new generation. Tellingly, perhaps, his idol is Marco Pantani, the Italian Tour and Giro d'Italia winner, who endured countless doping allegations and who ended his career a cocaine addict, dying alone in a hotel room in Rimini on St Valentine's night, 2004.

Christian Prudhomme, the Tour director, cited Ricco's positive test result as evidence that the war on doping is being won. Yet this claim has become too familiar. For all the tub-thumping lectures from race promoters who can see TV rights and sponsorship contracts dwindling as the kilometres pass by, the fight against doping appears never-ending. Even before this Tour began, Tom Boonen, the biggest star in Belgian cycling, tested positive for cocaine.

Bob Stapleton, the Team Columbia manager, has described the reliance of some riders on doping as an addiction. On this latest evidence, ten years after the notorious Festina affair, it is an addiction that is proving impossible to kick.

Cavendish - who is 147th in the overall standings, almost two hours behind Cadel Evans, the leader - remained typically upbeat. “I'm here for the sporting side of the Tour, not the political side,” he said. “I'm here to win. But I can see it's a massive disappointment for the organisers, even if it proves the tests work, and at least it's another person caught.

“I woke up this morning and thought I want to win today, and when I heard the news I still thought I want to win. From the sporting side it doesn't affect me.”