Next Tuesday, the Commons is due to hold a “meaningful vote” on the Government’s Brexit plan under the terms of the EU Withdrawal Act.  As matters stand, it will be presented with the same one that saw the biggest defeat for a Government in modern times, and the biggest backbench revolt by Conservative MPs in that period too.  In this event, Theresa May will be no more fortunate second time round unless Labour abstains or there is a sea-change among Tory backbenchers.  Neither is remotely likely.

If she loses, there is some suggestion that the Government will seek to bring the deal back in the event of a relatively narrow defeat (however defined).  However, the Prime Minister pledged in February that in the event of her deal being defeated in the Commons next Tuesday, the House will hold a vote on No Deal the next day and, if that proposition is then also defeated, will hold a vote on extension the day after.

It is possible that all three routes will be rejected, but as we write the most probable outcome is that the Commons votes against May’s deal, then against No Deal, and then for extension.  The logic of her position is that free votes will be granted next Wednesday and Thursday if votes take place  Whipping either way on either motion would bring resignations in its wake, and the Prime Minister’s main political objective at present is to avoid these.

If the House votes for extension, the EU will then respond.  As George Eustice, who writes on this site today, said in his resignation letter, this is likely to lead to “a sequence of events culminating in the EU dictating the terms of any extension requested and the final humiliation of our country”.

Whatever the terms and conditions of any such extension, May will then have either to concede indicative votes (as Philip Hammond and other have suggested) or have them forced on her by the Commons via Oliver Letwin and company.  Either way, the legislature, not the executive, would in these circumstances be conducting the negotiation, in effect, rather than judging it – a constitutional unknown.

We concede that possibility and likelihood are doing a lot of work in this analysis.  No Deal could still somehow slip through the cracks – not because Parliament votes for it, but because there is now a legislative presumption of leaving on March 29, and there may be some procedural twist that is unanticipated.  But it is hard to avoid the conclusion that the Prime Minister has less than a week to save what shreds of authority still cling to her and her windswept Government.