Jenson Button seems in jocular and enthusiastic frame as he admits that he is resigned to enduring a dismal Formula One season this year, thanks to his Honda's poor performance. “We are not going to win or get a podium place, I know that,” the Somerset-born driver acknowledges. So why the good mood? Partly it's due to his determined optimism for 2009, when a new car is promised, but meanwhile he has discovered a new outlet for his competitive energies: competing in triathlons.

With a third of the Formula One season now gone, 28-year-old Button is languishing at 13th in the drivers' championship, with three points. Undoubtedly it's tough for the man hailed on his Formula One debut in 2000 as Britain's next motor-racing prodigy, not least because Lewis Hamilton, the latest British boy on the block, is leading the field with 38 points in only his second season.

So if you're going to have a humiliating year in Grand Prix, why not find an impressive new sports hobby? On June 15, Button's tough regimen of running, cycling and swimming training takes him into a big new challenge, the Nokia Windsor Triathlon. The race, which takes place in Windsor Castle, Eton College and the River Thames, has been voted “event of the year” seven times by the British Triathlon Association and attracts serious competition.

There's another reason why Button's bounding energies need a new outlet. As befits any thrusting young Formula One star, Button has long been linked with a string of beautiful women, but now he appears footloose again. In February, he confirmed that he had split with his girlfriend of two years, Florence Brudenell-Bruce, who is the 22-year-old “face” of John Lewis and a descendant of the seventh Earl of Cardigan. Button had linked up with the model a year after splitting from his fiancée, the Fame Academy singer Louise Griffiths, three months before they were due to be married.

Button says he began triathlon training a year ago partly to boost his stamina and partly out of boredom. “I go to Lanzarote to train at the Club La Santa, which is used by Olympic athletes because it's warm all year round. They do mini-triathlons there, so I got into doing it.”

“Everyone was there to kill themselves”

To get race-fit for Windsor, Button competed at a small event last month in Sevenoaks, Kent. “It was great,” he beams. “Everyone was there to kill themselves, people breathing so hard they wanted to collapse. I came 16th out of 250 people. I was really happy with that.”

He's under no illusions about his chances next week, though: “I don't expect to be 16th at Windsor. My aim is to be in the top 10 per cent of the finishers. That will be difficult. It's pretty close stuff. But I'm all prepared. I've been training by riding the Windsor loop on my bike.”

The Windsor triathlon features a 42km cycle ride, a 500m river swim and a 10km circuit run. Up to 2,000 people participate. “There's some stiff competition,” says Button. “A good friend [the Olympic medal-winning rower], James Cracknell, is doing it, along with a pal of mine who does Ironman events. Cracknell is going to be pretty fit. There will be some professional triathletes, too.

“I wish I had more time for training because I'm flying a lot for the Grand Prix and that's quite tiring. But I've done a lot of biking down in the South of France. Recently my running has improved more than anything else. Swimming's the most challenging; it's technique as well as fitness, so it's the hardest to improve.”

It sounds a world apart from his early Formula One days, when he was publicly admonished by his Benetton team boss, Flavio Briatore, for his lax attitude and lifestyle (misdemeanours included driving a rival team's road car, a Ferrari, and getting caught doing 142mph on a French motorway). Briatore complained: “He needed to spend time with his engineers rather than rushing out to have his picture taken for a lifestyle magazine.” Was the criticism fair? Button grimaces: “In my first year with Benetton in 2001, I was not as fit as I should have been. I would not say I was a playboy - Flavio is a fine one to talk! But maybe I did not concentrate as much as I might have. I thought that the secret of Formula One was: drive the car, keep reasonably fit and you will do well. But you have got to be 100 per cent dedicated, not least to convince the team that you are worth making the effort for. My second year at Benetton was better, and now I'm completely into fitness and loving it...which is a bit sick,” he smiles.

Button's new-found fitness fanaticism also reflects the ever-increasing pressure on Formula One drivers to live like professional athletes. “A lot of drivers are working on their fitness. I would say I'm one of the fittest. Australia's Mark Webber takes it very seriously, too. He runs the Webber Challenge in Tasmania, a 350km charity challenge involving trekking, kayaking and mountain biking. I would love to do it.”

As well as triathlon sports, Button also prepares for the rigours of Formula One with core-stability exercises. “You feel a lot of what the car is doing; it throws you about. The vibrations are tiring, too. We do a lot of forearm and triceps work and neck-strengthening. If you are pulling 5G (five times the force of gravity) through a corner, your head feels five times as heavy. It's like having a small person sitting on your skull. The best training is to drive as much as you can, but it's not always possible.”

Pre-race diet is crucial, he adds. “I've always been pretty good. I don't eat puddings. What I do eat is natural and never too fatty. The Honda team has a Japanese chef who prepares sushi and noodles. I'm 6ft and 71kg, but I eat like you would not believe. You need a proper carb overload before a race. And we drink lots of fluids, starting three to four days in advance. Fluid intake during the race is essential, which is why some drivers wee in their cars. I don't ever feel the need. In Malaysia, the pump to my one-litre drinking-water bottle stopped working. After an hour in the car I started shivering and my vision got blurry.”

Button stresses that all this fitness work is not just about maximising his driving abilities, though: it also turbocharges his morale. “Training gives me a legal high. If I don't do a session a day, I get tired. In fact, I would like all of us drivers to take part in a fitness competition to see where we stand. Back in James Hunt's time, they used to do cycle races round the circuit for charity before the car race.” Given the way his current Honda car is competing, Button might not be much worse off pedalling round the circuits. “Well, things aren't as good as I would like them to be,” he acknowledges. “But things are starting to pick up. Even before we started racing this year we were talking about 2009. Things will change. We have a goal. We now have a proper technical leader in Ross Brawn.”

There would be one problem with cycling round the track, though; Button says that being perched on a saddle feels more dangerous than sitting in his Honda. “Formula One is far safer than ever, thanks to the efforts of the Grand Prix Drivers' Association and the FIA. They've done a great job,” he says. “I get more scared riding fast on a pushbike.”

“I've got great people around me”

Aside from fear, how about loathing? It can't be easy living amid the adulation of Lewis Hamilton, and the constant “Button-undone” headlines? But our man is adamant that he does not measure himself against other drivers' performances, only his own. And anyway, he adds, the press hasn't been that bad. “Last year, most of the reports about my season were positive. And I'm lucky that I've got great people around me who can point out that it's not all bad.”

Do they still include his father, John, a former rallycross driver who bought him his first racing machines and named him after the British car marque, Jensen? “Yes, the old boy still goes to the races,” he says. “He cares a lot about my racing, but he's not there to have an opinion.” Jenson may have outgrown paternal mentorship, but Dad is still around to offer staunch support, even when the sport doesn't involve cars. “He's definitely coming to Windsor - the whole family will be there. I might build them a grandstand,” Button says, laughing.

The Nokia Windsor Triathlon takes place on Sunday, June 15. Visit www.humanrace.co.uk