That's it. The end. Over. It's been a long, long road but Theresa May has finally run out of it. Her staying power has been creditable, or insanely stubborn, depending on your view, but this must be the final chapter in her premiership. It may also be the end for Brexit – at least as the hard Brexiteers understand it. Faced with the choice of a bad Brexit or no Brexit, they may have opted unconsciously for the latter.

At any rate, Brexit is now on a knife edge. Assuming Wednesday's vote happens as the Prime Minister promises, and parliament votes against a no deal, that should be the end of their dreams of a “clean break”/WTO Brexit in two weeks. MPs surely have the power to prevent such an outcome. On Thursday, if there hasn't been an election called, MPs should vote also for an extension of Article 50, and therefore put a brake on the UK's departure from the European Union.

Since no one in their right mind believes there is any point in just having another three months of this neurotic indecision, the extension would have to be long enough for the UK to have a general election and come to some consensus on what leaving the EU means. Or whether to leave it at all. That would surely take a year at least. Probably two.

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This would mean the UK paying many billions for the privilege of remaining, and having to elect MEPs to the European Parliament in May. That is a legal requirement for member states, and the UK would of course remain a full member of the EU pro tem. Such might be the sense of frustration and disillusion with Brexit, which is demonstrably a result of its advocates being unable to decide what it means, that this extension might turn into something rather more permanent.

My own view is that it would probably lead to Britain parking itself in the European Economic Area – the so called Norway option. This means the UK would be out of the political institutions of the EU, and the Common Agricultural Policy, but remaining in the European Single Market. This is an unsatisfactory compromise, since the UK loses its voting rights in the Council of Ministers, but it is undoubtedly Brexit. It has been good enough for Norway since 1994, and it may be the only compromise that works.

But at this moment, in the backwash of today's astonishing events, rational thinking on Britain's future relations with Europe is pretty well impossible. The government cannot govern, parliament cannot choose and Britain's political parties are disintegrating. The Tory Party is irrevocably split in all but name, and Labour already has.

It was left to the Attorney General, Sir Geoffrey Cox, to drive the last nail into the Prime Minister's coffin with his legal advice on her latest “breakthrough”. It was “bollocks” he said – at least that was his Tweeted censure to the Channel 4 presenter Jon Snow, who'd suggested that Sir Geoffrey had been bounced into changing his legal advice on the backstop. In fact, Cox hadn't changed his advice – at least not materially. His statement concluded that the UK, even under May's new deal, could be trapped indefinitely in the customs union backstop, albeit that the risk of this had been reduced. If Brussels behaved in bad faith, Britain could legally cry foul.

The Brexit Select Committee tried to make sense of this and ended up resorting to metaphysical speculation about the meaning of “bad faith”. This is an existential question, essentially, and one that the philosopher Jean Paul Sartre wrestled with all his life. The Brexit Secretary, Stephen Barclay, who is no Sartre, said that Britain could claim bad faith if there was “unjustifiable delay” beyond the agreed timescale for negotiating the future trading relationship. This is supposed to be completed by December 2020. But since no one ever took that date seriously, delaying beyond it could hardly be bad faith.

Anyway, by definition the European Union always conducts its negotiations in good faith. If there is still no technical solution to avoiding a hard border in Northern Ireland, how would a delay in the expiry of the backstop be in “bad faith”. The benchmark is surely the Good Friday Agreement and the British government's commitment to it. If the only way of honouring that is for the UK to remain in a customs union and in regulatory alignment with the Single Market, then surely “good faith” would indicate that the backstop should be permanent.

Theresa May had made two fatal mistakes. She thought she could rely on a legal solution to what is essentially a political problem. Lawyers confine themselves to the very strict meaning of words. The Withdrawal Agreement is legally binding, therefore there was never any way – in codicils, declarations or addendums – to undo what was already set in legal stone.

Her other mistake was to believe that she could keep her party united by placating the hard Brexiteers in Jacob Rees-Mogg's European Research Group. That was never going to work because they are essentially incorrigible. Like the followers of the Branch Davidian cult in Waco, Texas, they would happily go up in flames for their beliefs – and take the country with them.

This is a cathartic moment. The government and parliament has had to face up to its collective inability to resolve the greatest crisis faced by Britain since the Second World War. There is no leadership, no constructive thinking. Just a vacuum where political leadership should be. This would be an ideal moment for a charismatic figure to seize the moment and lead the country out of its confusion and disarray.

We don't do charismatic leaders anymore. We do Jeremy Corbyn, who never knowingly rises to an occasion. Or we do Boris Johnson – who remains the most likely to succeed Theresa May if she falls in the near future. There could be no better illustration of the state we are in, than that choice.