I've written a cover story for this week's Spectator called 'Plan B for Boris' in which I speculate about the Mayor of London's chances of becoming the next leader of the Conservative Party. Boris's best hope would be if David Cameron lost the next election – a scenario that would probably put paid to George Osborne's leadership ambitions, given that he'd be held partly responsible. Of course, Boris would have to be an MP in 2015 in order to throw his hat into the ring. Does that mean it could only happen if he lost the mayoral election next year? Not necessarily. There's nothing in the rule book to prevent Boris from standing for Parliament whilst also serving as mayor, as Dave Hill revealed last year: “The GLA tells me there is no legal or constitutional impediment to Boris subsequently becoming Mayor Johnson MP.” Let's not forget that Ken Livingstone remained an MP for a year while also serving as mayor. (To read more, click here.)