The greatest government defeat in parliamentary history strikes when you draw mutually incompatible red lines and pretend you haven’t. When you spend three years lying to the faces of your colleagues and the voters who elected them. When you vastly overestimate your power and political capital and dismiss the interests and negotiating strength of your closest allies. When you behave as though a minority government is an absolute monarchy. When, through a combination of hubris and ineptitude, you fail to engage in even the remotest dialogue with your opponents on the country’s gravest political debate of the last 75 years. Tuesday night’s result, above all, is what happens when you pretend something agonisingly complicated is in fact painlessly simple. Theresa May could have lost the vote on her Brexit deal by a majority of 600 and it would still not have delivered the humbling she deserved.

History will deal with the prime minister, but history must wait until after 29th March. Parliament is now locked in a race against time to assert its power over the government. It will first attempt to ensure we cannot leave the EU without a deal. Then it will attempt to force the government to request an extension to Article 50. The prime minister is all but guaranteed to cave on both. Parliament is in the end a question of arithmetic, and May no longer has the numbers to continue blackmailing her colleagues with the threat of economic oblivion. She will therefore have to declare an explicit policy not to crash out, and recognise that there is no time to approve all the relevant withdrawal legislation before our departure date—not least because the first task is to secure approval for a deal which parliament just rejected by 230 votes.

The EU will in all circumstances approve an extension if the government knows why it is requesting one. No individual member state wants a no deal scenario that will hurt its own economy and citizens. More to the point, no member state will be prepared, at the last minute, to abandon Ireland. If our government requests an extension, the Irish government will ask any wavering colleagues to agree to it.

And so we must determine the reason we are seeking such an extension: ratification of a deal, second referendum or general election. The Opposition has now tried and failed to secure a general election in this week’s no confidence vote. Assuming no further attempts succeed and the prime minister does not call one herself, that leaves just two options.

So what is the deal we could ratify? The EU has insisted that it will not alter the legally binding part of the withdrawal agreement. Even if it did, it would make no difference.

This is a question of ruthless logic and colliding interests. Put simply, what makes the backstop unacceptable to MPs is what makes it acceptable to Brussels and Dublin: that is, the UK’s inability to terminate the arrangement unilaterally. If you make the backstop unilaterally breakable, the EU will not accept it. If you leave it unchanged, parliament will not accept it. If you fudge the wording to kick the can further down the road, you sacrifice trust and neither side will accept it. This was, or should have been obvious the moment May agreed to the instrument in December 2017. Ultimately it amounted to a political death warrant with a year-long time delay.

This is, in any case, no longer about the backstop. Numerous Labour MPs have rejected the deal through its insufficient commitment to existing rights and protections, many Tories object to the £39bn unconditional divorce settlement, and perhaps two dozen prefer to have no deal at all. It was in the service of this last group that the prime minister for two years directed her entire strategy. Yet as anyone with a passing interest in British politics might have foreseen, zealous Europhobes will never be placated or satisfied. In a worldview that abhors compromise, the first side to concede pragmatism is the first to surrender. It is why they respond to fresh chunks of meat not with restraint but hunger. Suffice it to say the EU will not risk the Good Friday Agreement to bail out a moribund British prime minister for the sake of exceptionalists whose raison d’être is to reject reality.

How then can May’s deal be delivered when it appeals to so few MPs for so many reasons? Even if we assume that parliament can ultimately be persuaded to vote through the legally-binding text on a backstop and divorce bill, there is no guarantee that it will accept an amended political declaration on the future relationship. A commitment to negotiate a permanent customs union might bring over some Labour MPs, but would drive out large numbers of Conservatives, for whom the lure of global free trade (and, latterly, UK-only trade deals) is a primary article of faith. The risk of a Conservative split is real. Meanwhile the second alternative of a “Norway Plus” scenario in the single market and customs union would constitute an even greater heresy. May has successfully persuaded her party that the free movement of people amounts to political betrayal and cultural anathema. The Norway model’s loss of existing democratic oversight would cause further outrage.

That leaves us with a second referendum—its question, time-frame and consequences both unknown and, for now, unknowable. This option remains the likeliest of a series of unlikely outcomes, but at the moment only a slim minority of MPs are backing it. Any Brexit decision demands parliamentary numbers, and halting it altogether demands political courage.

Whatever happens in the weeks and months ahead, we can be assured of one thing. None of the old rules any longer works. People and events now routinely defy the political laws of physics. The prime minister sees her signature policy trounced by the widest margin in history and, instead of resigning, declares the policy will not change. Her party inflicts an unprecedented humiliation on its leader and the following day unanimously votes to keep her in post. Parliament and the executive tussle over an improvised constitution as, for the first time in generations, the Speaker finds himself at the fulcrum of British politics. Theresa May’s reckoning will soon approach. British democracy’s may arrive much sooner.