Despite having initially experienced some discomfort in the cockpit of his new office - the McLaren-Mercedes MP4-25 - reigning F1 World Champion Jenson Button has now professed himself 'very happy' as the 2010 world championship campaign approaches apace, and ready to give it '100 per cent'.

Having joined McLaren from Brawn GP - now Mercedes Grand Prix - over the close-season, Button has had a limited period of time in which to adapt to his new surroundings and gel with the team. The British star's first laps inside the MP4-25 around Valencia's Circuit Ricardo Tormo early last month were perhaps predictably hampered by an ill-fitting seat that took some time to be adjusted to his liking, as the 30-year-old languished some 1.5 seconds shy of the outright pace on his first day in the car, and a lowly fifth out of seven drivers on the timesheets [see separate story - click here].

Since then, however, the Woking-based outfit has worked hard to adequately accommodate the sport's most recent title-winner, and on the final day of the second test at Jerez de la Frontera in southern Spain a fortnight later, Button was able to remind everybody just why he has the number '1' proudly adorning the nose of his car by leading the way.

As he prepares to set off for Sakhir for the curtain-raising Bahrain Grand Prix in the desert kingdom in just over a week's time, the seven-time grand prix-winner is exuding confidence and positivity - and ready to kick-start the defence of his hard-fought 2009 drivers' world crown in style.

"Really good," Button told Radio, when asked how he feels inside the car now during a special pre-season Vodafone McLaren-Mercedes phone-in session. "We've done a lot of work on the seat and moving bits in the car out of the way so that I can fit, and I'm very comfortable now, very happy.

"It's been really good, actually; they've really listened to what I've had to say and adjusted things immediately, and it's amazing how quick we've been able to get new carbon seats built - it's only taken a few days, which is very surprising.

"I want to be 100 per cent for the first race. It took us a little while, but you would expect that, because last year they had two drivers who were three or four inches shorter than me, so it's never going to be easy - but I'm really comfortable in the car now, so no complaints."