There is an operation in progress by Tory Brexiters to persuade fellow backbenchers to write to Graham Brady, chair of the 1922 backbench committee, calling for a vote of no confidence in Theresa May as leader of their party.

This is what one of them told me:

'I’m campaigning myself. We need 60-70 letters, not 48... I know people who are putting letters in today. I think we are the closest ever to her going and I think, thank God, this could be it.'

The reference to 48 letters is the threshold for triggering the vote. But this MP wants a comfortable margin above that, so that the PM can see that a sizeable number of her colleagues want her to go.

This is not an exquisitely centralised and coordinated campaign against her. It is an emotional outpouring, largely by Brexiters, that May’s version of Brexit betrays what they see as the most important prize of leaving the EU, namely 'taking back control'.

But in the words of another their ilk, the coup will only work if what he calls 'the agnostic centre' of the party rise up against her in partnership with the Brexit True Believers - not because they see her as treacherous, but because they’ve lost confidence in her ability to deliver an orderly Brexit.

I’ve spoken with some of these agnostic Tory centrists, and although they have nothing good to say about May, they are not posting their letters.

Why not? Because they cannot coalesce around a successor.

The Brexiters are touting David Davis as a caretaker PM, to steer the UK through Brexit and then stand down - and to give the Tory Party time and space to identify the appropriate leader to take them into the next general election.

But Davis is Brexit marmite: his opponents are as numerous as his fans. One influential Tory said: 'I voted for David twice in previous contests. Sadly I have come to the conclusion he cannot unify this party.'

This is a week of maximum vulnerability for the PM: she may, after all those many weeks of rumour and backbiting, face a formal challenge to her leadership. But I wouldn’t count on it. And even if she does suffer that rudest of insults from members of her own team - the triggering of a formal vote on whether she stays - don’t expect her to Trexit (copywrite RP) quietly.

As one of sternest critics put it to me: 'does she seem like a quitter to you?!!!!'

This article originally appeared on Robert Peston's Facebook page