Being from the Isle of Man, Cavendish's accent is closer to Scouse than Glaswegian but, like the original cheeky chappy (James McFadden), "gallus" is another fitting description for the most exciting British cyclist to emerge in years.

Only two years ago, the then 20-year-old Cavendish was winning a gold medal on the track at the Commonwealth Games in Melbourne – with Scotland's James McCallum claiming bronze – but now he starts next Saturday's Tour de France as the fastest sprinter in the race, and one of the most talked-about personalities in the sport.

Fastest in the race doesn't mean Cavendish will win overall, incidentally. It refers simply to his lightening finishing speed – his main asset being a sprint that seems almost certain to bag him a stage win or two in the opening week, when the flat stages tend to come down to huge, and terrifying, bunch sprints. In the recent Giro d'Italia he won two such stages and could have had three had he not, in a rare but shrewd act of selflessness, gifted one to a team-mate.

Cavendish is outspoken, he is incorrigible, and he is a breath of fresh air. David Millar, the Scot who is now one of the Tour's elder statesmen, struggles to suppress a smile at the mere mention of his name. And then he tells a story that reveals something of the paradoxical character of his young fellow Briton, who combines awesome self-assurance and confidence with occasional bouts of anxiety.

A week into last year's Tour – which Cavendish started, riding the first 11 days for experience – he pulled alongside Millar. It was the first Alpine stage and Cav was in trouble; the peloton had just negotiated a climb that had him struggling at the back, in the danger zone. And then he made a fatal mistake: he looked at the little computer on his handlebars that told him how much power he was generating just to keep up. The number on the screen terrified him. He knew he couldn't sustain that effort for five minutes, never mind the five hours of the stage. So he sought out Millar in the pack.

"Jeez Dave, you should have seen the power I was producing on that climb," Cavendish told Millar, whose response was that of the seasoned pro. "Tsk, tsk," he said, or words to that effect. "This is the Tour – and the first rule of the Tour is you don't look at your computer: that's a schoolboy error."

Later, Cavendish appeared alongside Millar again. "Look Dave," he said, pointing at his handlebars, and his computer screen, now covered with black tape.

Taking Millar's advice to heart, but aware that he didn't possess the self-discipline not to look at the screen, he had dropped back to his team car and asked the mechanic to cover it, so he couldn't see what it was telling him. Millar was impressed. But also amused.

Cavendish's antics tend to be like that. Earlier this season, at the Tour of California, he lined up in a field that included the Italian sprinting legend, Mario Cipollini. Cipollini was a star of the 1990s and early 2000s, winning countless stages of the Tour and Giro; and he too was flamboyant and outspoken. Yet in California – where the 40-year-old was making a comeback – he was humiliated by Cavendish, who, as he caught the Italian in a time trial stage, removed his foot from his pedal and rode past him with one leg.

Cipollini looked on aghast, and castigated the young British rider at the finish for his lack of respect. "He probably hasn't figured out how to behave," said Cipollini. "I don't think it's clever to do that to a rider like me. He's fast but he's still a kid."

Cavendish starts his second Tour on Saturday, with the aim of winning stages and then – in all probability – retiring at half-distance, to save himself for the Olympics, where he will team up with Bradley Wiggins in the Madison. Having won the world title in Manchester in March the British pair are favourites.

On the back of his Giro stage wins, his confidence is sky high. "To be a winner you have to be an alpha male," he explains. "But in a team environment you can't (always] afford to be an alpha male, you have to be a leader, and appreciate those supporting you. I appreciate every bit of work my team-mates do." Hence his gifting of a stage to his team-mate, Andre Greipel, in the Giro. It was, says Cavendish, a "thank you" for shepherding him in the final kilometres of each stage.

Cavendish says that his Giro stage wins "are worth four or five of my wins (from] last year". A Tour stage would be worth twice as much again. He claims that it isn't that he is a better rider this year, but a more confident one. "I've always had the ability to handle myself in bunch sprints – I've never been scared," he says. "But the Tour is like no other race. The sprints are a completely different style and all I know is that my wins show that I am the fastest there.

"But that doesn't mean anything if I'm not in the best position."

Which is complicated in the Tour due to the sheer number of sprinters, and their teams, jostling for position in the hectic finishes. Yet Cavendish's path to possible glory looks a little clearer than it did a couple of weeks ago, thanks to the absence of Tom Boonen – the Belgian having been barred after testing positive for cocaine – and the injured Italian Daniele Bennati.

Winning a stage in the Tour, says Cavendish, "would be the biggest thing that could ever happen to me, without a doubt. It would not only confirm what I have already done – which is to show I am the fastest – but raise me up a level, to being one of the great sprinters. To be that you have to win Tour stages. I am ready for it."

If he proves as ready as he thinks he is then there is no doubt that Cavendish will be in even more demand than he currently is.

Already one of the hottest properties in the sport, it is rumoured that he has had offers for next year that will make him a millionaire – in euros, at least. Currently he is contracted until the end of next year to Team Columbia – the former T-Mobile squad – but he is likely to be the marquee signing for the planned new British professional team, which aims to start the 2010 Tour de France and produce a "clean British winner" within five to 10 years.

The British performance director Dave Brailsford is behind the plans, and this week he called Cavendish "the Wayne Rooney of cycling – one of the key characters in the sport in the next 10 years".

After the doping scandals of the past two years, the Tour organisers would probably welcome an opening week dominated by headlines about Cavendish, who has said of drugs cheats: "They are robbing people – they should go to prison in my book."

"You get people who will cheat in all sports," he added. "But you also get people with talent who don't cheat."

Included in their number – as he would be the first to point out – is Mark Cavendish.

TOUR DE FRANCE 2008: THE MAIN CONTENDERS

IN THE absence of last year's winner, Alberto Contador, whose Astana team has not been invited, this year's Tour de France is wide open – the only certainty is that there will be a first-time winner.

CADEL EVANS, Australia Tour pedigree: finished second to Contador last year.

Evans is not flamboyant, but he is brave and reliable and grinds out results. If he lives up to his status as favourite he'll be the first Australian to win the Tour.

ALEJANDRO VALVERDE, Spain Tour pedigree: beat Lance Armstrong in the toughest mountain stage of the 2005 Tour. Otherwise, sixth last year.

A sometimes controversial figure for alleged links with alleged dodgy doctors, Valverde is a class act from Murcia who has enjoyed fine recent form, winning the Tour warm-up, the Dauphine Libere.

ANDY SCHLECK, LuxembourgTour pedigree: debutant.

With older brother Fränk (who recently plunged down a ravine in the Tour of Switzerland, but was okay), Andy rides for the strong CSC-Saxo team, led by consistent Carlos Sastre. After finishing second in last year's Giro d'Italia, though, many fancy the 23-year-old to spring a surprise in his first Tour.

DAMIANO CUNEGO, Italy Tour pedigree: best young rider in 2006

Still only 26, Cunego's win in the 2004 Giro d'Italia established him as the most promising rider of the new generation. Several disappointing seasons later, he seems back on track. An attacking rider who thrills the Italian 'tifosi'.

RICCARDO RICCO, Italy

Tour pedigree: 20th last year.

A stick-thin climbing specialist – à la Marco Pantani – 24-year-old Ricco rides his second Tour fresh from finishing second in the Giro d'Italia, and is sure to make his presence felt. A supremely confident figure, 'The Cobra' – as he likes to be known – is renowned for disparaging his opponents and promoting himself as "the future of cycling". Hugely entertaining.