Whitmarsh: Title is now Button's

That is the view of McLaren team principal Martin Whitmarsh, who thinks that the 15-point advantage that Button holds as he heads into Japan is big enough to ensure he is the man who will succeed Lewis Hamilton as title winner.

"It is not the most exciting way to win the championship, but I think you have got to score the points," said Whitmarsh about the impact on Button's fifth placed finish in Singapore.

"Jenson is under a lot of pressure and when you have not won a world championship there is enormous pressure there, especially if it is your team-mate who is challenging you.

"I think he did a solid job here and one has to say, I don't think it is mathematically done yet, but it looks like he has got the championship, which is a fantastic achievement."

He added: "It is not easy to win a championship, whatever advantage you start with by way of a car. He obviously had a decent flying start to the season, but he did a real solid job to make sure he was in a position to take that championship."

Button has experienced great highs and lows during the season - with a dominant start to the season that saw him win six of the first seven races followed by a poor spell where he has struggled to finish on the podium.

Although that form has not been helped by his Brawn GP car struggling to get heat into its tyres, Button has also had to keep his nerve as his title rivals started cutting away at his lead.

Whitmarsh has acknowledged that things have not been totally straightforward for Button, but says that does not detract from the job he has done in 2009.

"I think he has wavered a little bit in truth, but I think he has been around some time, he is a very smooth driver, an intelligent driver and all he had to do was keep his head and he was going to win the championship given the start he had," explained Whitmarsh.

"I am sure he will go away from this event feeling more relaxed. He will still have some tension, as it is very easy to crash out at the next event with Rubens winning, which will be a 10-point swing - and we've been there, the last two seasons have been like that for us. He just has to stay calm, and if he does not make any mistakes he will win, but that in itself brings tension to you."

Whitmarsh has also said that he is not surprised Button has found it hard at times to keep up the form he showed at the start of the year.

"With a championship, particularly for someone like Jenson who has been around a long time and may feel that this is his one opportunity ever in his life to fulfil his childhood ambition, that is enormous, enormous pressure," he explained. "I am pleased for him, it will be great for him to relax and I am sure he can cruise to the championship win."