Towards the end of the Channel 4 drama Brexit: The Uncivil War which was broadcast last Monday evening, the leaders of the rival Remain and Leave campaigns meet in a central London bar. By coincidence Craig Oliver, David Cameron’s then director of communications, and Dominic Cummings, director of Vote Leave and inventor of the slogan “take back control”, spot one another across platforms at Moorgate tube station. They had regular rows when they worked as Tory advisers before the campaign began and have been at daggers drawn throughout it. But both are physically and emotionally exhausted as voting day approaches and – in an encounter Oliver has insisted was fictional – they agree to talk over a pint.

It is shortly after the murder of Labour MP Jo Cox by a right-wing extremist in her West Yorkshire constituency. Oliver clearly feels things are slipping away from Remain. Sitting opposite his foe, the look on his face betrays his grim and growing realisation that Cummings is winning the war and heading for a stunning victory with unimaginable consequences for the country – albeit, he feels, by employing the basest of campaigning methods.

“You’re feeding a toxic culture where the very notion of evidence-based truth is dead, where one side never believes the other, no one listens any more, we just yell,” Oliver says. Twitching a little, Cummings replies that Leave “had to yell, to be heard” and adds that the binary “in” or “out” question on which the British people would vote within days was always going to force people “into tribes”.

Oliver then says his greatest fear is that the tribal divisions which the campaign has already established will become permanent. “I worry it won’t heal.”

Earlier on Monday, before that broadcast, ugly scenes – of exactly the kind to which Oliver had alluded in the film – were playing out outside the House of Commons. And, in this case, they were all too real.

Anna Soubry, the Tory MP and Remain campaigner, was mobbed by far-right pro-Brexit campaigners who yelled that she was a “Nazi”, a “traitor” and a “fascist”. The indomitable Soubry was shaken by the hostility that Brexit had fostered. In the House of Commons there were calls for the police to do more to protect MPs caught up in the feverish atmosphere created by Brexit.

Anna Soubry and pro-EU activist Femi Oluwole are surrounded by pro-Brexit supporters including James Goddard, far left, who was later arrested. Photograph: George Cracknell/LNP

Two days later Soubry was equally horrified when the outspoken columnist Brendan O’Neill mocked a fellow MP for invoking the memory of Cox during a podcast in which they all took part. “I was on [this Sky News podcast] with [Labour MP] Jess Phillips discussing the problem of how to get women into public life – which is very real, a hugely important subject – and Jess mentioned Jo Cox,” Soubry tells the Observer after the incident. “And then this deeply offensive man – who if they had told me beforehand was on it, I wouldn’t have gone on, so I was already cross – he said: ‘Oh, to use a murder for political purpose’. And I lost it.

“How dare he? We are talking about something that actually happened. It was clearly linked to the far right, which some of these people who are roaming outside parliament are, and he kept belittling it. This is a very present threat. It is not protest – they are thugs.”

It was not just outside parliament that democracy had gone awry and turned sour. On Wednesday in the House of Commons – totally deadlocked on Brexit with just over two months to go until the UK is due to leave the EU – there was constitutional uproar.

The speaker John Bercow had controversially allowed an amendment that will force Theresa May to come up with a Brexit Plan B within three days if the prime minister’s crucial meaningful vote is lost on Tuesday. On the government front bench five cabinet ministers, including May, Julian Smith, the chief whip, and the leader of the House, Andrea Leadsom, sat shaking their heads in fury at Bercow.

Pro-Brexit MPs shouted about “constitutional outrage” and claimed Bercow was biased. One Labour MP observed later that “anarchy had spread from outside to inside the mother of parliaments”. Rather than parliament “taking back control” – which was what Brexiters had insisted Brexit was really about – it seemed to have completely lost it.

When Cameron announced in January 2013 that the British people would be able to vote in a referendum on whether the UK should stay in or leave the European Union he assumed this great exercise in democracy would settle the decades-old argument for good.

“It is time for the British people to have their say,” he said at the time. “It is time to settle this European question in British politics.” Many predictions by politicians and commentators over recent years have proved wildly wide of the mark, but none, perhaps, more so than this. This weekend, two and a half years after the UK voted narrowly to leave the EU, and as Tuesday’s crucial vote on May’s Brexit deal approaches, nothing is settled at all. Divisions in Westminster and the country are deeper, wider, and more visceral than ever. Our parliament, to which Brexiters want to return sovereignty, is gridlocked and unruly to the point of paralysis. At the point when its decisions are most urgently needed, it is unable to agree on a way forward.

“The political bubble has never been polarised like this before,” says Kenneth Clarke, the Conservative former minister, father of the House of Commons and a lifetime pro-European. “It’s a tragedy ... a parody of democracy.”

With May facing seemingly inevitable defeat this week, Clarke, who will retire at the next election after more than five decades at the forefront of politics, cannot see a way out of an interminable mess he never imagined could develop, and fears things will get worse before they get better.

Some people roaming outside are clearly linked to the far right. It isn't protest – they are thugs Anna Soubry MP

From his lofty position as parliament’s wise old man he is also scornful of the prime minister. “It was always the plan of government to lose this first vote [on Tuesday] and then raise the Project Fear stuff,” he says. “But what do we do if [May] gets up in front of the House again and says: ‘The sky will fall in if we don’t vote for this deal’ and all this crap? If she comes out and says there is no deal now, she will have a lot of ministerial resignations and I don’t quite know what will happen then.”

On his office wall Clarke, a survivor of European arguments that scarred, and in the end did for, the premierships of Margaret Thatcher and John Major as well as Cameron, has a framed copy of a 2017 front page in which he and 14 colleagues were notoriously branded Brexit mutineers. He considers it a reminder to keep going. But he fears the current prime minister simply has no idea where she is going. “The key events now are: what is Theresa May’s reaction to this three-day deadline she’s got?,” he asks. “Will she actually tell anybody what her Plan B is, beyond her rather lightweight entourage? I would be faintly appalled if I learned she wasn’t even turning her mind on what to do.”

When Soubry reflects on the wider politics and the impact on her party she, too, is scathing about May and says she has never known times so uncertain and turbulent. “It is an utterly remarkable time,” she says. She believes the prime minister is trying to force her deal through the house despite the huge risk of ending up with a no-deal Brexit that many in her own cabinet have admitted would be economically catastrophic. It is a kind of political suicide mission. “Her tactics are to run the clock down deliberately,” Soubry says. “I think she’s prepared to crash out without a deal.”

But would that not spell the end of the Conservative party, and disaster for the country with it? “I agree, but she’s prepared to do it,” she says.

There is one thing, however, that has brought together MPs on all sides of the Brexit divide – even Soubry and May. She reveals that the prime minister – “who I have no relationship with” – sent her a handwritten letter about the abuse against her outside the Commons.

“Dear Anna,” it reads, “I hoped to see you in the House today, but I wanted to write and say how sorry I was to see the treatment you received near parliament yesterday. That was appalling and no one should be subject to such abuse.”

Soubry continues to read aloud. “We all know there are differing views, often very strongly held on the European issue, but everyone should be able to put their views without the risk of intimidation and abuse. I know you are a robust person, but incidents like this are unsettling and I’m sorry you were subject to such behaviour. Yours ever, Theresa.”

Despite such occasional shows of solidarity between opposing sides in parliament, arguments over Brexit are all that newer MPs have known during their times as parliamentarians. Layla Moran, the first ethnic minority Liberal Democrat MP, who has been serving the voters of Oxford west and Abingdon since 2017 and is pushing hard for a second referendum, says she’s exhausted by it all and now regards it as the norm.

For her there is no respite and the fear of what may lurk outside the safe interior of the Palace of Westminster is ever present. “We’re in the situation where we’re all in campaign mode,” she says. “It feels like we’ve been on the precipice of a general election for the whole time I’ve been an MP; we know we’re in the middle of a moment of history that will be written about, but not knowing what happens next is making it really tense and emotional.” She fears for her safety and that of others. “They’re bruisy men out there. You’d cross the road at night if you saw them.”

Outside parliament the yelling from both sides of the Brexit argument continues. In recent weeks dozens have lined up with banners, flags and placards by mid-afternoon every day. The activity ramped up in the weeks before Christmas. “That’s when the yellow jacket lot first came,” confirms a policeman outside Black Rod’s garden last week.

Has it made his job much harder? “Well it’s not got easier,” he sighs in the cold. Behind him, and dotted in pairs across Westminster, at almost every entrance and gate, are police armed with machine guns.

I can't understand why people want it. We all have phones. We're all connected and have friends and family all over the world Andy Curzon, engineer

Andy Curzon, an engineer from Manchester, finds it “crazy that many people, including MPs, are incapable of understanding the basic facts of trade and that we’re going to sever these links.”

He waves an EU flag next to a sign for passing cars that reads “TOOT TO STOP BREXIT”. Asked whether he has talked to any of the Leave protesters today, Curzon sighs. “You try but ... nationalism now is just crackers – I can’t understand why people want it. We all have phones. We’re all connected and have friends and family all over the world.”

Two male Ukip protesters, who won’t share their names, blame “fake news”, under which they classify all major media, with no exceptions. “Leave means leave. We’re not unreasonable,” insists the younger man, dressed in a parka and blue jeans. He describes himself as “a citizen journalist from southwest London”. About the Soubry incident, he is flippant: “This is a Westminster bubble, that’s how people talk in the pub. Get used to it. There is no such thing as hate speech, it’s just different opinions. I find your paper offensive. I won’t shut you down or get you arrested.”

On the street, the man still bellowing a full-throated “out means out” is enraged by a host of conspiracy theories he believes in. “I find news the way I need to find it,” he says when asked about his information. “I research people that I get it off. If I can get it from a family member then that’s it. If you were on my side, you’d be doing all that.”

The country should prepare for riots, he says. “They can’t expect the people to be law-abiding citizens when government is as corrupt as it is. All them people in here,” he claims, “are getting paid backhanders all the way through the system.”

Former prime minister David Cameron took a gamble that backfired spectacularly. Photograph: JASON LEE/POOL/EPA

On 23 June 2016 the British people voted by 51.9% to leave the EU and 48.1% to stay in. Cameron’s gamble not only backfired by delivering a Brexit vote which forced his resignation and set the UK on a road out of the EU, but his hope that a referendum would lance the European boil has been exposed as appallingly misplaced – for the precise opposite has happened.

The British public is now more divided, more aware and more conscious of who is on which side of the argument at the heart of British public life. Politicians, communities, families are – 31 months on from the vote – unable to come together and seem largely immune to persuasion, unbiddable and unwilling to budge from entrenched positions. The country stands just 75 days away from the supposed moment of Brexit but with no national or political consensus over what Brexit should entail, or whether it should go ahead at all.

Deadlock in parliament reflects division in the country. “Brexit has paralysed the democratic system,” says a senior Tory MP. “And the really alarming thing is I cannot see how this does not endure for decades. We will all be defined as Remainers or Leavers for decades to come. This is not a passing argument. It really is close to civil war.”

Normal alliances have broken down, and parties have split many ways, raising questions about whether Brexit will deliver a new political alignment, in the form of new party in the centre and at the extremes. “The real legacy of Brexit could be a completely different British politics and party system,” says a Labour frontbencher.

Cameron’s referendum has left the Conservative party split between hard Brexiters, soft Brexiters, and Remainers, while Labour, although its membership and supporters are overwhelmingly pro-Remain, has its own deep divides.

Its leader Jeremy Corbyn seems unwilling to commit to what most of his party wants – a second referendum – because he is a lifelong Eurosceptic. Labour has staggered through the last two and half years with a policy of deliberate ambiguity in order to offend the fewest possible of its supporters.

Outside the party system, there are two broad camps, fairly evenly split, if the polls are to be believed. On the one side are those who believe that because the country voted for Brexit it must go ahead with it – either because they think it is a good thing instrinsically or that not to do so would be dangerous for democracy, or both. In the other camp are those who believe that we should find a way out of activating Article 50 and stay in, perhaps by holding a second referendum with Remain on the ballot paper or by simply cancelling the whole project.

Prominent supporters of both sides have been turning up the rhetoric before next week’s vote in the hope of winning the day. Yesterday the pro-Brexit cabinet minister Chris Grayling said blocking Brexit could end the 350 years of “moderate” politics that Britain has enjoyed since the English civil war. Last week leading businesses, including Jaguar, Land Rover and Ford, warned of job losses, while Greg Clark, the business secretary, said a no-deal Brexit would be economically “disastrous”. This week, the Brexit saga and uncertainty will enter another phase.

What will happen if May’s deal is voted down – as it almost certainly will be – nobody knows. Downing Street is determined to press ahead with the vote, although it is aware that the prime minister is facing a massive defeat – another indication of how impossible her position has become. What then?

“We could head for a no-deal Brexit, but Parliament voted last week to block that option off as it would be catastrophic,” says a senior Tory MP. “We could have a second referendum to sort out the mess, but there is no sign of a parliamentary majority for that either. So God only knows.”

Outside the Commons the protests go on. “This is civil war without the muskets,” says Helen Slater, who has come from Bristol to campaign. “It is appalling.”