Jenson ButtonJenson Button says he is left with mixed feelings about leaving the Brawn GP team, but the World Champion claims it was something that he had to do.

Button clinched his first world title with the Brackley, UK-based former Honda Racing team this year, but decided to move to McLaren for 2010 to partner Lewis Hamilton. The World Champion insisted he needed a fresh challenge after reaching his goal with Brawn, but admits he is sad to be leaving the team he has been with for seven years.

"It's something I felt I needed to do in my career," Button told AUTOSPORT. "Everything has always been aimed at winning the World Championship, as it should be, and with Honda or Brawn as it is now, we achieved that goal in 2009.

"I'm very excited, but also very sad to leave a team that I've been with for seven years. But all good things come to an end and we ended on a high."

The Briton, who picked up two awards at the AUTOSPORT Awards in London on Sunday, said he is finally getting used to the idea that he is the World Champion.

"After the race in Brazil, it was an emotional moment and I was just knackered basically," he said. "I'd run out of steam because it was so stressful. Then you go through weeks of just waking up and not realizing what you've achieved, other days you wake up and realize I've achieved my goal – I am World Champion.

"When you spend so much time away from racing, which I've done in the past few weeks, to come to the awards really brings the emotion back and it's a perfect way to celebrate the season. I have a couple more awards ceremonies and sports personality shows on Sunday, so it's a pretty intense and exciting week."