"First of all, Hamilton appears to have lost faith in McLaren's ability to deliver world championships.
"Secondly, Mercedes have pitched him a hard sell - they have argued that Ross Brawn is building a similar dynasty with them to the one he built with Ferrari, who dominated the early 2000s under him.
"They want to build that dynasty around Hamilton. They have also offered slightly more money than McLaren and more freedom to do personal sponsorship deals. It's quite a gamble, though, for a man who professes he 'just wants to win'."