David Cameron vs Boris Johnson - it's getting personal

Prime Minister makes thinly veiled attack on the London mayor as he outlines his EU reform deal to the Commons Credit: PA

It's getting personal.

In a Commons statement which was always going to be a challenge for David Cameron, his MPs sat quietly - as their leader ran through his list of achievements at last week's EU summit.

But never was the cheer bigger than when he mentioned the forthcoming EU referendum: bigger than when he said he'd got the UK out of "ever closer union"; bigger than when he said he'd cut benefits for EU workers.

But given most of those sitting behind him are planning to campaign on the opposite side - to Leave the EU - we should not be hugely surprised.

It shows quite how difficult the next four months are going to be for Mr Cameron.

At the end of his statement, there was one MP, more than any other, to whom David Cameron was talking: Boris Johnson.

"I have no other agenda," the Prime Minister said referring to his decision not to stand for re-election in 2020, "than what is in the best interests of our country."

In other words: this decision is not about my future, it's about the UK's future.

He didn't look at the London Mayor as he said it - but everyone in that chamber knew who he was talking about.