On Monday night, the Brexit virus contaminated its own opposition. The people who spent the past three years fighting the project to get Britain out of the European Union suddenly started behaving exactly like those they had challenged. It was like some kind of zombie infection broke out in Westminster, passing from person to person, until, at the end, the characters you trusted turned around, with blood-red eyes, and started trying to bite your head off.

It came on a night of high political drama. These evenings used to arrive once every few years and pass into legend. They now happen about once a day.

Britain has entered a period of prolonged political hypertension: Members of Parliament and journalists are fatigued, making generation-defining decisions in a heated environment on a merciless timetable against a background of online and offline abuse, and accusations of treason.

Time itself seems to be slowing down so that weeks now feel like they last for months. By midweek, journalists covering the debate talk about events on Monday as if they happened years ago. Brexit is like a black hole, sucking in time, light and matter.

There are no other news stories. There are no other considerations. There is nothing but Brexit, and it is driving everyone mad.

On Monday, MPs took control of the process from the Government. It was the latest battle in a bout of constitutional trench warfare between Parliament and the executive, the likes of which we haven’t seen since the English Civil War in 1642.

The House of Commons voted to temporarily cancel something called Standing Order 14 — a rule that used to give Downing Street control over the legislative timetable — and then started sitting on their own terms to debate whatever they like. It was like a drab British version of the Tennis Court Oath at the start of the French Revolution.

Having seized the agenda, MPs used the time to hold a series of nonbinding indicative votes on what Brexit policy should be. There were four options to choose among:

•• Membership of the European customs union, which controls taxes on goods crossing borders

•• Membership of the European single market, which harmonises regulations across the Continent

•• A second referendum to ratify whatever deal was passed with the European Union

•• A push for the Government to simply revoke Article 50, the legal mechanism for leaving the EU, and call the whole thing off

That fourth option may well be where this whole sorry mess ends up.

But for the time being, it is still not considered politically palatable — the word “revoke”, while popular with “remainers”, is completely toxic to those who are terrified of being seen as undermining the much mythologised “will of the people” as expressed in the Brexit referendum.

So it didn’t have a chance on Monday. But the other three choices had solid backing and could have succeeded.

The first two were put forward by MPs who accepted Brexit but wanted to limit the damage it would do to the British economy. The third was put forward by those who wanted to stop it altogether.

Critics of Brexit have been split between these two approaches — damage limitation and outright reversal — since the referendum first passed. Together, they have the numbers to put forward an alternative plan with majority backing. But apart, they are just large minorities.

The results were a disaster. Everything failed. The customs union plan lost by 276 votes to 273, the single market by 282 votes to 261, and the second referendum by 292 to 280. In each case, they would have succeeded if these two groups had worked together. In each case, they refused to do so.

After they were read out, Nick Boles, the Conservative MP who authored the single market plan, stood and addressed his fellow lawmakers.

“I accept I have failed,” he said. “I have failed chiefly because my party refuses to compromise. I regret therefore to announce I can no longer sit for this party.”

And with that, he walked away. A voice called out after him: “Oh, Nick. Nick, don’t go, come on.”

But he did not turn around. He literally crossed the aisle and went to sit alone, a newly independent MP. Boles was one of the architects of the modernisation project of the Conservative Party, where moderate figures in 2005 attempted to cleanse it of its more jingoistic and hardline policies.

His departure was proof that initiative was now dead. It had been massacred in Brexit’s nativist spasm, in which nationalist zealotry trumped any other form of right-wing political discourse.

But the symbolism went even farther than that: he was accepting that the very concept of pragmatism was impossible in his party.

This is the Tories, the single most successful and long-lasting political party in the Western world.

It is sunk in a mire of crazed puritanism. Anyone who refuses to go along now either leaves of their accord or is forced out.

On vote after vote on Monday, the Tories simply boycotted the process and abstained. They scorned every compromise position, every articulation of a middle ground.

It wasn’t because they supported Prime Minister Theresa May. They won’t vote for her deal in sufficient numbers to get it through, either, which is why it has failed each of the three times she has brought it to the floor.

But what’s terrifying about the closing days before the latest deadline of April 12 approaches is that such puritanism is no longer restricted to the government benches.

It is now present among the opponents of Brexit, too. Labour MPs who support the People’s Vote campaign for a second referendum refused to back proposals for a softer Brexit on Monday, as did the moderate Liberal Democrats party.

Even the Independent Group, a newly formed collection of former Conservative and Labour MPs who self-define as willing to work across traditional tribal loyalties, refused to support it.

The same applied to many proponents of a softer Brexit.

All they had to do was offer support to the People’s Vote campaign as a ratification process on their plans and they could have secured much wider backing for their proposals, but they would not do so. Everyone called for everyone else to compromise, while never seeming willing to do themselves.

So instead, it turned into a circular firing squad. All the options lay dead on the floor. It was like Parliament had asked a bunch of infants to solve the Prisoners’ Dilemma.

Why is this happening? How is a country that was once famed for its moderation, stability and practical judgment turning into a political abattoir?

The answer is identity politics. Brexit is a right-wing culture war conducted in populist terms. It is not really about the EU at all.

It is about people’s sense of who they are. It is about wanting a world of walls, separating out people and ideas and political structures from each other. But it is not just a desired outcome: By now, it is also a way of doing things.

The Brexit mindset does not compromise or accept caveats. It is politics in primary colours. There is victory or national slavery, and nothing in between.

The Brexiteers’ desired outcome has not been accepted by liberals and internationalists. But they seem to be increasingly infected by the methodology of Brexit, by its manner.

On Monday, they behaved exactly in the uncompromising winner-takes-all approach of the people they are fighting. British politics has changed from “the art of the possible” to a battle of true believers.

It leaves the country in an extremely perilous situation. The Government’s latest wheeze, expressed in a statement from May on Tuesday night, is to extend Article 50 again and try to bring opposition leader Jeremy Corbyn on board to see if they can find a deal that works for both Labour and the Conservatives.

But even this attempt, which shows an openness the Prime Minister has not exhibited before, faces the same problems: if the plan does not include a People’s Vote, Corbyn loses a chunk of his supporters, inside and outside Parliament.

If it includes a soft Brexit, those People’s Vote types still won’t support it, and May loses most of her own party in the bargain. Whichever way you look at it, political puritanism makes the mathematics of a Brexit majority hard to imagine.

The country is stuck, frozen in indecision. Parliament is re-enacting the end of Reservoir Dogs. And still the clock ticks mercilessly down. Puritanism has provided no answers whatsoever, except pain and failure.

Unless MPs quickly rediscover Britain’s tradition of pragmatism, things are about to get very ugly indeed.

• Ian Dunt is the editor of Politics.co.uk, the author of Brexit: What the Hell Happens Now? and a host on the Remainiacs podcast