After threatening to resign many times over the last two years, David Davis has finally gone and done it.

The man who once said there would “be no downside to Brexit, only a considerable upside” has left the government.

To paraphrase Boris Johnson, the ex-territorial SAS man quit because he was unable to polish Theresa May’s turd.

The agreement reached by the cabinet on Friday at their Chequers Awayday, which would see the UK effectively remain in the single market for goods, would result in Brexit not meaning Brexit, Davis wrote in a brutal resignation letter.

"In my view the inevitable consequence of the proposed policies will be to make the supposed control by Parliament illusory rather than real,” he told May.

"As I said at Cabinet, the 'common rule book' policy hands control of large swathes of our economy to the EU and is certainly not returning control of our laws in any real sense."

He added: "At each stage I have accepted collective responsibility because it is part of my task to find workable compromises, and because I considered it was still possible to deliver on the mandate of the referendum, and on our manifesto commitment to leave the Customs Union and the Single Market."

"I am afraid that I think the current trend of policy and tactics is making that look less and less likely."

What might do in for May more than any other, was his line suggesting the Prime Minister could yet soften Brexit further.

"I am also unpersuaded that our negotiating approach will not just lead to further demands for concessions," he writes.

The hardline Brexiteers in the European Research Group won’t like that.

Will they force her out?

For there to be a leadership challenge, more than 48 of May’s MPs would need to write letters to the chair of the Tory backbench 1922 committee, saying they no longer had confidence in the Prime Minister.

May will address her MPs this evening in a bid to see that off.

What she has going for her is that there seems to be no natural successor who could unite the party.

Tory MPs will look at Boris Johnson, at Jacob Rees Mogg, at Jeremy Hunt and all the other possible contenders and think, could they do better?

Also, we’re supposed to have reached a deal with Brussels by October. That’s three months away. A summer leadership contest would properly screw that up.

What about a snap general election?

Scottish Labour’s Richard Leonard says it is in the “interests of the great majority of people in Scotland and across the United Kingdom” for their to be a General Election.

Which is brave considering Labour are still behind in the polls.

A YouGov poll for the Times put the Tories on 41, Labour 40, and the Lib Dems on 9.

The SNP who, unlike Labour, haven’t selected candidates for the seats they lost last time round, have so far resisted those calls.

Ian Blackford is instead hoping May will use her statement in parliament this afternoon to “recognise the clear majority in parliament for the urgent need to keep the UK in the single market and customs union”.

That seems unlikely.