Boris Johnson - Member of Parliament?

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Media captionDavid Cameron: "I love Boris"

"Absolutely." With that one word David Cameron has lit a fire under the idea of Boris Johnson standing for Parliament at the next election.

The question the prime minister was responding to was whether Boris could return to the Commons whilst remaining Mayor of London.

Moments earlier he said it would be "great to have Boris back in the Commons". He also told reporters: "I love Boris."

Contrast that with Boris's prevarication last night on Newsnight when he was asked again and again about his plans

Jeremy Paxman: "You've definitely ruled out any return to Parliament?"

Boris Johnson: "I've got a very heavy and demanding job to do"

Jeremy Paxman: "for two and a half years…"

Boris Johnson: "..and I'm doing it to the best of my ability and I think that we're achieving a great deal in London…"

And so on and so on until in despair.

Boris Johnson: "I think this is now a super-masticated subject…"

Jeremy Paxman: "Well masticate a little more...spit it out"

Boris Johnson: "What I would rather do is get on with my job of running the city."

David Cameron said in public today just a little of what I am told he has conveyed to his old school friend in private.

The Tory leader has told Boris that if he wants to run for Parliament the party leadership will help him in any way they can and stressed that his chances of becoming Tory leader one day depend on helping the current leadership win an election not waiting for them to lose.

The argument is that the Conservative Party are unlikely to want to replace a losing Old Etonian with one who is slightly older.

The two men and their families met at Chequers recently for a rapprochement lunch.

As well as singing a memorable version of Gangnam Style and playing family football they discussed politics at great length.

It's even suggested that Mrs Johnson - Marina Wheeler - told her husband to think about the merits of the prime minister's position on an EU referendum. The two men text most days and speak at least once a week.

It's clear why Team Cameron are suing for peace now. Boris is their biggest electoral asset - particularly with first-time voters.

If they had simply waited for him to make up his mind on whether to run the risk was that he would, once again, overshadow his party's message.

A decision to stand for Parliament would be seen as the act of a man waiting for a leadership vacancy - the act of a vulture waiting to pounce.

Boris allies are making it clear that he has not made his mind up yet and that he would turn down a big job, such as party chairman, if it were offered.

Some fear that they are being set a trap by Team Cameron. If Boris now refuses to run he will look unwilling to help his party. If he does run he will be tied to Cameron's success.

Time for Boris to masticate a little more and a little faster.