We’ll easily cope,” breezes the no-deal prime minister. “This is a great, great country.” Indeed it is. Most inhabitants would certainly agree. But to love your country is not to think it greater than others, nor incapable of making grievous mistakes. Britain has not, as yet, made the fateful error of actually electing Boris Johnson and his cabinet of undesirables. Nor did it vote for a no-deal Brexit. But on he drives, accelerating towards the abyss.

It’s that insouciant ignorance that drives businesses mad; the devil-may-care fecklessness, ignoring the boring details. Andrea Leadsom, our improbable business secretary, writes in the Sunday Telegraph that she has met firms of all kinds and guess what? “They were overwhelmingly positive about our future.” She ends: “Britain’s best years for business and for all our people lie ahead.”

All three of these very different businesses make the same complaint. No one listens. They can’t get the ear of any ministers

Andrew Varga was driving along when he heard David Davis laughing on the Today programme as he expounded similar airy nonsense about the “trusted trader scheme” – goods checked in warehouses away from the border, all easy-peasy.

“I was climbing the wall! Drives me to despair!” says Varga, managing director of Seetru, a Bristol manufacturer of industrial safety valves. Perhaps Leadsom has only met happy businesses by refusing to hear from those like Varga, a Cambridge engineering PhD, who has failed to find a hearing with any branch of government for the inconvenient facts from companies like his.

“My local Tory MP, Michelle Donelan, wouldn’t come to the factory: when I saw her in her surgery she couldn’t get rid of me fast enough.” Labour MPs have listened and visited but no Tory to date. At a large meeting with Suella Braverman, then Brexit minister, she parroted the usual empty phrases: “trusted trader” and “WTO rules”. Since 2016 he has been trying to raise the alarm, but “no one wants to know”. He wrote to the prime minister, who passed it on to Steve Baker, then at the Department for Exiting the European Union, but got a useless stock reply.

At one time his exports were growing fast, with 130 employees and eight apprentices training to high standards, but since the referendum things have quickly changed. “Some EU customers instantly decided it was too much trouble and switched to EU manufacturers – we lost 10% of the business.” Others with his valves embedded will cut them out next time they redesign their machines. To trade in the EU he needs to obey rules of origin, recording every raw material, tracking every component, requiring “horrendous” new IT systems, his various valves containing 30,000 different configurations and “tripling our admin workload”. New security rules require fencing and guards round his perimeter with checks on staff, costing millions. Delays due to checks “are anathema to our just-in-time customers. They give us three chances: late once is a warning, twice is a final warning and then you’re out.”

Q&A What does a no-deal or WTO-rules Brexit mean? Show If the UK leaves the EU without a deal it would by default, become a “third country”, with no overarching post-Brexit plan in place and no transition period. The UK would no longer be paying into the EU budget, nor would it hand over the £39bn divorce payment. The UK would drop out of countless arrangements, pacts and treaties, covering everything from tariffs to the movement of people, foodstuffs, other goods and data, to numerous specific deals on things such as aviation, and policing and security. Without an overall withdrawal agreement each element would need to be agreed. In the immediate aftermath, without a deal the UK would trade with the EU on the default terms of the World Trade Organization (WTO), including tariffs on agricultural goods. The UK government has already indicated that it will set low or no tariffs on goods coming into the country. This would lower the price of imports – making it harder for British manufacturers to compete with foreign goods. If the UK sets the tariffs to zero on goods coming in from the EU, under WTO “most favoured nation” rules it must also offer the same zero tariffs to other countries.

WTO rules only cover goods – they do not apply to financial services, a significant part of the UK’s economy. Trading under WTO rules will also require border checks, which could cause delays at ports, and a severe challenge to the peace process in Ireland without alternative arrangements in place to avoid a hard border.

Some no-deal supporters have claimed that the UK can use article XXIV of the General Agreement on Tariffs and Trade (Gatt) to force the EU to accept a period of up to 10 years where there are no tariffs while a free trade agreement is negotiated. However, the UK cannot invoke article XXIV unilaterally – the EU would have to agree to it. In previous cases where the article has been used, the two sides had a deal in place, and it has never been used to replicate something of the scale and complexity of the EU and the UK’s trading relationship. The director general of the WTO, Roberto Azevêdo, has told Prospect magazine that “in simple factual terms in this scenario, you could expect to see the application of tariffs between the UK and EU where currently there are none”. Until some agreements are in place, a no-deal scenario will place extra overheads on UK businesses – eg the current government advice is that all drivers, including lorries and commercial vehicles, will require extra documentation to be able to drive in Europeif there is no deal. Those arguing for a “managed” no deal envisage that a range of smaller, sector-by-sector, bilateral agreements could be quickly put into place as mutual self-interest between the UK and EU to avoid introducing or to rapidly remove this kind of bureaucracy. Martin Belam

This is not just about the bottom line. There are emotional shocks too. “Our EU customers were our friends, but there was a sudden chill after 2016. I hear antagonism, nationalism rising, as if we are ‘other’ and not one of them any more. My people are upset by conversations with old customers who say: ‘You bloody Brits! You’re ruining everything, and we’re not going to pay the extra duty.’” His office staff are remainers, but the factory floor is split in half. “Everyone tiptoes around each other or it gets too heated. The Brexiters are aggressive, the remainers creep into their shell.”

His father praised 1972’s entry into the common market. “Fantastic. Overnight just one gold standard for every product exported to every European country instead of a plethora of kite marks.” When Brexiters castigate EU regulations, “they have no idea how good they are for us”. Varga is a “congenitally liberal Tory, but I can no longer support that party”.

‘At a large meeting with Suella Braverman, then Brexit minister, she parroted the usual empty phrases: “trusted trader” and “WTO rules”.’ Photograph: Jonathan Hordle/ITV/REX/Shutterstock

Talk to others in quite different trades and the crescendo of despair rises as “do or die” day nears. Chris Slowey, head of Manfreight, a hauliers in Northern Ireland with 300 employees and 120 indirect jobs, lists just some of the crises ahead: they take Kerry Foods from the Republic to places like Leeds, but with a no deal “taking just one quiche across the border needs three vet certificates, for the milk, the ham and the eggs. That’ll take five times more vets and they’re short already.”

He needs customs agents, who are in short supply. He buys 40 HGVs a year from Europe. “Each will cost £16,000 extra in tariffs, plus 16% on parts.” Here’s what just-in-time means for food deliveries – exactly 47 minutes from factory to ferry, two hours and 10 minutes crossing and eight hours max to stores in Leeds. “Any delay and drivers have to stop and take a break, but food has a short shelf-life.” He fears British stores will stop sourcing from Ireland – and until the Operation Yellowhammer leaks, neither he nor his Freight Transport Association had any warning of possible fuel shortages. “Just let them see what happens when customers can’t get what they want, people used to strawberries on Christmas Day.” And here’s Val Hennessy, director of International House, a large English language school in Bristol where Brexit is already “a disaster”. Five jobs have been lost so far. “Europe is our main market, lovely students bringing lovely money to Britain, a great export. But they sense they’re not welcome, they think we’re a bit xenophobic, a bit fascist – and they might need a visa. So they go to Ireland, whose schools are booming.”

All three of these very different businesses make the same complaint. No one listens. They can’t get the ear of any ministers. No one wants to know what Brexit is doing already, or the devastation no deal will cause to companies like theirs. They warn that bogus reassurances about the UK’s preparedness will come unstuck. Lorry delays at ports may be sorted within weeks, but Varga says his problems are mostly “frog-boilers” – the steady loss of customers that has started already. Why hasn’t business shouted louder from day one? He tried, but others took fright in the face of hostile press coverage. He says businesses were warned that pro-leave customers would turn their back on products from companies that spoke out against Brexit.

What these businesspeople share is sheer incredulity at what is happening, at politicians charging ahead deliberately remaining ignorant of the damage done. Expect the mighty £138m public information campaign to be empty propaganda. HMRC promises to contact “every known trader”, but why bother when they refuse to hear what they’d rather not know? Gordon Brown rightly calls for parliament to hold an independent inquiry into the consequences of a no-deal withdrawal, as Keir Starmer and the former head of the civil service Lord Kerslake demand that MPs be given all the facts.

The prime minister threatens not to honour our EU debts, which would guarantee that no free trade deal could ever be signed. But, he says, none of this is for parliament to decide. As we head towards the cliff-edge, it seems only this most cavalier and feckless of prime ministers is allowed to “take back control”.

• Polly Toynbee is a Guardian columnist