Back me, get Boris? Why May's pledge to resign if her deal is passed will lose her crucial Labour votes

So now they know. If Labour backbenchers vote through Theresa May's Brexit deal, they may end up with Boris Johnson in charge of Britain's future.

The prime minister's announcement yesterday that she would resign if her deal gets through parliament means that a hardcore Brexiteer may well lead the government through the critical second stage of Brexit talks.

It's true that May often reneges on her pledges. But it's hard to see how she could possibly survive going back on this one. Too many of her MPs are desperate to see her go.

Her announcement was a gift for the European Research Group (ERG) of pro-Brexit Tory hardliners—but a slap in the face for Labour MPs in Leave-voting seats looking for a reason to get Brexit over the line.

Indeed, the new leader may actively pursue a kamikaze No Deal strategy for Great Britain, with Northern Ireland alone within the backstop. Far from being a safe option in a crisis, May's deal has instead become a Pandora's box.

Nothing sums up the myopia of May's Brexit strategy like the fact that she announced the end of her own career to get her fanatical backbenchers on board, having only offered Labour constituencies loose change that would barely reverse a single year's worth of this decade of savage council cuts.

She threw a feast for her own side to gorge on and gave Labour backbenchers leftover bones to gnaw at.

But not only did the scraps fail to do the trick with Labour, but the feast hasn't sated the ERG. Having briefly turned his coat to back the prime minister yesterday, Jacob Rees-Mogg announced last night that he couldn't support her deal after all as the DUP wouldn't back it. (Maybe today he'll tell us which private school he learnt that one at.)

When witnessing all this, it is worth bearing in mind that Militant Labour councillors—for all their bullying and ultimately their incompetence—were fined and banned from public life for defying government spending cuts.

Members of the ERG have lied their way through the Brexit referendum, lied throughout negotiations, destabilised the government to boost their own leadership chances, held the country to ransom to oppose policies they once supported, driven Britain to the edge of an economic and social cliff, and in some cases personally profited from the chaos they have deliberately wreaked.

For all this, most will remain unscratched, their seats in parliament secure. The British ruling class was never taught the Latin word for “consequence.”

The Independent Group's decision last night to oppose all options except a referendum and revocation was a reckless gamble that paid off; the People's Vote option unexpectedly survived.

The risk now is that Continuity Remain will pursue it with a bloody-minded vigour mirroring that of the ERG, driving all other options off the table and wrecking the chances of any consensus emerging next week.

But May's antics have made consensus around her own deal even less likely. In the kind of self-defeating chicanery that will come to be her epitaph, her stunt won over few in her own party while repelling the opponents she needs to bring on board.

Pragmatic MPs remain in a bind. If they vote for a softer Brexit or a second referendum next week, they may need to maintain control of the parliamentary agenda for the foreseeable future to ensure the prime minister—whoever it may be—does not deliberately scupper whatever is agreed.

All we know for sure is that May's deal, like the woman herself, is not the route to strong and stable.