David Cameron enters EU referendum fray

Listen very carefully - you just might hear the sound of a third, yes a third, campaign joining the arguments about whether the UK should stay in, or run for the EU exit.

OK it's not an official campaign, but it's leader, is already well known - our prime minister, who, until today has been hanging back from the fray.

The case - they want you to vote to stay in if they improve our relationship with the rest of the Union. But if the next few months don't go their way, well, they might just ask you to leave. This unofficial campaign, run from number 10, may as well be called, "reform, or we might just cut and run".

For months the PM has said he's concentrating on his attempts to get a better deal for the UK, and has avoided getting into the nitty gritty of the in or out debate. But with anxieties in government that those who believe in exit are gaining ground, that changes today.

David Cameron has directly challenged the suggestion, put forward by some Eurosceptics, that we could slip prosperously into a relationship with the EU like Iceland, or Norway - a trading friend but not a full partner.

That's not the official position of the Vote Leave campaign, who claim today's intervention shows Number 10 is panicking.

That's denied by number 10.

But the prime minister arrives at this summit in Iceland with a new tone and a new tempo to his arguments.

One minister told me that, at the very least, you have to look as if you're trying.

The difficulty, of course, is that David Cameron's message is nuanced - let's stay in if certain conditions are met; if not, he is ready to tell you to do the opposite.

Hardly a clear slogan a spin doctor would desire but now a message that Mr Cameron will try to sell.