Boris Johnson's deceptively humble announcement that he will "try to find somewhere to stand in 2015" (his search, one suspects, won't be in vain) finally brings an end to the will-he-won't-he saga of recent years.
Boris's allies have long argued that he could wear two hats at the same time, as Ken Livingstone did when he remained the MP for Brent East during his first year as mayor. But should the Tories be defeated at the general election, with Boris standing in the subsequent leadership election (his principal motivation for returning), the situation becomes more difficult.
To many, it is inconceivable that he could serve as both Conservative leader and Mayor of London. One option would have been to stand down before the end of his term in May 2016, but Boris today pledged to remain at City Hall for a full four years. Unless any leadership contest is delayed, he will struggle to justify wearing three hats (Mayor, MP and Conservative leader). For this reason, Boris's ideal scenario may actually be a Tory victory in 2015 followed by Cameron departing after the in/out EU referendum in 2017.
Then again, what are promises from him anyway? (As he puts it, "My policy on cake is pro having it and pro eating it".) Provided that any Conservative leadership election is delayed until six months before the end of his term, his deputy will take over and a costly by-election will be avoided.
For now, however, the Mayor is giving nothing away. Asked today whether he wanted to return to parliament to become Conservative leader, he replied:
No, what I said was … I'll revert to the kind of weasel mode here … What I said was, you've got party conference coming up in two months' time, you can't have this thing going on endlessly. Let's go back to Europe. I've said what I have to say. It may all go wrong but the likelihood is I am going to have to give it a crack.
Boris won't say he'll stand for the Tory leadership is the new Boris won't say he'll stand as an MP.