McLaren has confirmed that Jenson Button will join them on a "multi-year" deal, after Mercedes failed to agree to terms with the world champion.
Button will partner 2008 world champion Lewis Hamilton in a dream team to rival Ferrari's line up of former world champion Fernando Alonso and Felipe Massa, while McLaren retain the numbers 1 and 2 on their cars.
Although unconfirmed by McLaren, it is believed Button has signed a three-year deal worth £18m, before lucrative sponsorship opportunities.
Despite winning the world championship for Brawn GP at the penultimate race of the season, Brawn (now the rebranded Mercedes Grand Prix team) refused to meet Button's demands for a pay raise, leaving McLaren to swoop after their own negotiations with former driver Kimi Raikkonen stalled.
On the move, Button said: "So, although I won the World Championship with Brawn GP last year, and I’ll never forget that, I was always adamant that I wanted to continue to set myself fresh challenges.
"I’ve followed the McLaren team ever since I was a small boy, and it feels unbelievable to finally be a part of it.
"Also, I think it’s fantastic that we’ll be forming an all-British line-up. I know that we both fly the flag with pride, and I sincerely hope we can make the whole of the United Kingdom, as well as Vodafone McLaren Mercedes fans across the world, proud."
Raikkonen, who had admitted his 2010 plans were McLaren or nothing, is now expected to take a sabbatical, walking away with a reported £17m salary from Ferrari for the year, with leading world rally teams Ford and Citroen interested in the Finn's services.
Outgoing McLaren driver Heikki Kovalainen is now looking for a new team after two seasons with the Woking outfit, while Button's replacement at Mercedes could be Nick Heidfeld, who would partner fellow German Nico Rosberg.