JENSON Button may have joined McLaren for the challenge but he is adamant he no longer has anything to prove to anyone, not even to himself.

For the first time in his career, Button starts the season with the coveted number one on his car, the figure emblematic of the fact he is the reigning world champion.

It is a fact that hit home yesterday when he and Lewis Hamilton pulled the wraps off McLaren’s new car, the MP4-25, at the UK headquarters of the team’s primary sponsor, Vodafone, in Newbury.

Sceptics have questioned the wisdom of Button’s decision to quit Brawn GP, with whom he won the world title last season, and go up against Hamilton, who has been part of McLaren for the last 12 years.

The British duo, who make Formula One history as it is the first time a team has started a new season featuring the two most recent winners of the world title, insist only teamwork will assure one of them of continuing Britain’s recent dominance of F1.

As far as Button is concerned, the question is in moving to McLaren whether he felt the need to prove himself against the driver many believe is currently the best in the business.

‘‘I think winning the world championship and being the best in the world in that season is what we are all here to do,’’ said Button.

‘‘When you’re eight years old and looking at Formula One drivers and one becomes world champion, that is what you want to achieve.

‘‘That is what I achieved in 2009. This year, as I’ve said, I’ve looked for another challenge and that is exactly what I have on my hands.

‘‘I am as excited as I’ve ever been ahead of a new season, but not looking to prove anything to anyone.

‘‘I don’t need to do that. I don’t need to prove anything to myself because I am pretty happy with where I am in my life right now.

‘‘I am in the best position I possibly could be. I’ve the experience of winning the world championship in 2009, which is a boost to my confidence.

‘‘I’ve also gained a lot of experience and, as a person, I’ve become a lot more confident than last season.

‘‘I am in the best position I possibly could be.’’ That is undoubtedly to Button’s advantage, yet he is disadvantaged by the fact he only started work at McLaren at the turn of the year and is still getting to know the team.

As Hamilton remarked after unveiling the new car, which is a radically different design to past McLarens, he has had considerable input into this new model.

But if he and Button are to be world-title contenders, they have to work together, a situation he concedes failed to materialise in 2007, when he was up against Fernando Alonso.

In his debut year, Hamilton and the Spaniard were polarised, which cost both them and McLaren dear as Kimi Raikkonen won the title by a single point.

Asked how to avoid the recurrence of such a situation, the 25-year-old replied: ‘‘All I can say is I think we can work together more.

‘‘In 2007, perhaps in some cases, we (Hamilton and Alonso) didn’t work together well enough and we didn’t work together for the team.

‘‘I think we both understand we need to work together to push the team forward.

‘‘Of course, we want to beat each other, to get to the end of the year having won the constructors’ championship and one of us having won the drivers’ championship. I think we both understand that.’’ It was three-times champion Sir Jackie Stewart who remarked Button was entering the lion’s den, and that it was a mistake to be going up against a driver people perceive to be McLaren’s de facto number one.