Anthony Hamilton, the father and manager of Lewis Hamilton, blundered awkwardly into his son's career yesterday by swiftly putting a stop to a spontaneous charity bet that Hamilton Jr had taken on in good faith.

Hamilton Sr kept himself out of the limelight last year, but he is playing an increasingly interventionist role in the McLaren Mercedes driver's life as his second, more difficult, season in Formula One unfolds. Only two weeks ago, Anthony was complaining bitterly about what he considered to be unfair press criticism of Lewis's errors on the track, views that he conveyed in no uncertain terms to his son, who then spoke himself about what he called the “crap” in newspapers.

Now he has stopped a challenge to compete in a triathlon for charity, which Hamilton had taken on in response to a good-natured offer from Jenson Button. In a terse, one-line statement that stunned officials at McLaren, Hamilton Sr said: “Lewis has accepted the challenge like the good sport he is, but his manager has decided to withdraw him from it.”

The challenge arose during a press conference at Silverstone in the build-up to this weekend's British Grand Prix, when the two British drivers were sparring over Hamilton's claim this week that he believes he is fitter than Button. Unfortunately for Hamilton, the Honda driver is probably in better shape than at any time in his career after competing three weeks ago in his first triathlon.

Button got his own back on Hamilton by making him commit, in front of the Formula One press corps, to taking part in a triathlon at the end of this month. Button suggested that the loser should give £10,000 to the charity of the winner's choice.

Hamilton first tried to laugh off his claims of superior fitness, then found himself with no way out. David Coulthard, the veteran Red Bull driver, who announced yesterday that he will retire at the end of this season, mischievously egged on his fellow Britons in what was one of the most entertaining of public exchanges between drivers in Formula One for years.

Hamilton: “I've noticed that Jenson has a bit of a belly and so ... I was only joking. I was just trying to be positive.”

Button: “They're called muscles.”

Coulthard: “Place your bets and go and win the fight.”

Hamilton: “Well you've just done some event recently. What was that?”

Button: “It was a triathlon.”

Hamilton: “Yeah, I'm not sure whether I could do a triathlon so I'm not going to say that I could beat him at that, but generally I work my arse off. You work your arse off to be fitter than me, and you've got to believe that you're fitter than me and same way the other way round...It would be good to have a challenge.”

Button: “I'm sure we can work something out there. If you don't like triathlons ... the good thing is that you've got three different activities.”

Coulthard: “Run a lap of the track.”

Button: “Exactly, we could try different things. I've got a triathlon on July 27 if you're interested.”

Hamilton: “Where's your strongest point?”

Button: “Umm, all of them! And yours? We could do it for charity, I'm sure, as well. Yeah?”

Hamilton: “Yeah? Well shall we get this ... ”

Button: “We'll get DC [Coulthard] in there as well.”

Hamilton: “Yeah, get DC as well.”

Coulthard: “I'll be the referee.”

Hamilton: “You can be the bottle-holder.”

And so it went on, with Hamilton getting ever deeper into the mire and eventually having to confirm that he would turn up in Bath in three weeks for a 1.5-kilometre swim, a 40-kilometre bike ride and then a 10-kilometre run. The McLaren driver even got his BlackBerry out to see if he was free. “I was just checking my calendar so I wasn't being rude,” he said. “I was trying to see whether I'm busy that day and unfortunately I don't think I am ... but man, I'm up for it, I'm up for it.”

Much as he may have been game for what could have been a ratings winner for Hamilton's image and for Button's, the decision to extricate him was made swiftly by Hamilton Sr, who was not present at the press conference and gave no further explanation for his decision. He may have been concerned that Hamilton might get injured or that a triathlon could leave him exhausted a week before the Hungarian Grand Prix. Equally, he may have been worried that his son would lose to Button, by a very long way.