Andrea Leadsom could have resigned last summer with David Davis and Boris Johnson over the Chequers Plan.  Or she could have quit with Dominic Raab and Esther McVey during the autumn over the draft Withdrawal Agreement.  Instead, she stayed on in Cabinet, alongside fellow EU referendum leavers Liam Fox, Michael Gove, Chris Grayling, Penny Mordaunt and (later) Steve Barclay.  So why has she resigned today?  And why have they not – at least yet?

Let’s try to answer the second question first.  As Andrew Gimson reports on this site, Conservative MPs believe that Theresa May announce her resignation as Party leader over the weekend after meeting Graham Brady on Friday.  That would allow her to pre-empt, and attempt to draw the sting from, the European election results before they are announced on Sunday evening.

This take could be wrong.  But even if it is, the Prime Minister has clearly lost the confidence of most Tory backbenchers and Ministers alike.  The immediate reason is the terms of the proposed EU Withdrawal Bill.  Cabinet members insist that they did not approve, at yesterday’s meeting, all the contents of May’s speech yesterday – especially the proposal to legislate for a second referendum if the Commons votes for one.

It follows that the publication of the Bill risked the resignation of any of those Ministers named above, and perhaps others too – and that the House will not approve its contents in any event.  Which helps to explain why it is now very unlikely to be issued.  And why the Prime Minister – given the stasis that would fill the consequent gap – now has little alternative but to quit before the ’22 Executive, her Cabinet or both finally force the issue.

So those other Ministers perhaps think that there’s no need for them to quit – because May will have to do so first. But Leadsom is in a slightly different position to them.  As Leader of the House, she has a certain responsibility for the Bill.  She writes in her resignation letter that she could not tomorrow, presumably in the weekly Business Questions, “announce a Bill with new elements that I fundamentally oppose”.

Hence her resignation – which comes with a deadly sideswipe, first, at Downing Street for not allowing the proper scrutiny and approval by Ministers of recent Brexit proposals; and, second, at Philip Hammond (it seems) for advocating “policies contrary to the Government’s position.  Her long-time friend and supporter Tim Loughton has been tweeting criticism of Downing Street today.  That looks like an early warning signal of Leadsom’s intentions.

She thus becomes the latest of almost 50 Ministers to have quit May’s Government.  On the one hand, her critics will claim that her resignation is deliberately timed to boost a second leadership bid.  On the other, Leadsom’s refusal to hang on for a few more days can be seen as admirable – and principled.  Her job was one that she grew into and did well.  It could just be that the next Minister to depart will be none other than the Prime Minister herself.