“Car crash!” exclaimed managing director Andrew Varga, whose Brexit progress I have been following since the referendum. News of the latest Brexit U-turn landed on him on Tuesday out of the blue. All his years of preparation for a new UK product safety mark, all his thousands of pounds wasted, all the uncountable hours and effort were rendered pointless, at a stroke. Think, he says, of the great opportunity cost of that time and money, fruitlessly frittered instead of being invested in innovations and sales.

The government slipped out the news that it has abandoned a new product safety mark, UKCA (UK Conformity Assessed), which was intended to certify that products were checked to UK standards. The Brexiters rejected 30 years of using the European CE mark (whisper it, but it stands for the awful Conformité Européenne), recognised worldwide as a gold standard. All for what? Out of pure Brexit mania so that nationalist Britain would have its own, forcing double inspections. What’s more, all EU suppliers or exporters to the UK had to apply for the new UKCA mark, a strong disincentive to trade with the UK.

“You can wrap the new Brexit red tape three times around the world,” an exasperated manufacturer once said to me. Mark this: there was no actual difference in standards between UKCA and CE. Britain didn’t dare lower its regulations – nor raise them either. Yet again, pure Brexit ideology has crashed headlong into reality, facts overwhelming fantasy.

The government sneaked this out when their headbanger Brexiter MPs couldn’t plot in summer-vacated Commons’ corridors; no minister had to utter the words that the CE is now Britain’s standard again. What price sovereignty now, as Britain becomes the obedient rule-taker where once we sat at the table as fellow rule-makers with a useful veto in our pocket?

I have talked regularly since the referendum to the managing director of Seetru, which makes industrial safety valves in Bristol. Varga, a Cambridge engineering PhD, tried in vain with others to warn the government what creating a separate UK product safety mark would do. The referendum result caused him an immediate 10% loss of business. “Some customers instantly decided it was too much trouble trading with the UK, and switched to EU suppliers.” He has to obey EU rules of origin, obliged to prove the provenance of every raw material and component for each of 30,000 different configurations of his products, “tripling our admin workload” and requiring “horrendous” new IT systems. Delays, to his just-in-time customers, are “anathema”. “They give us three chances: late three times and you’re out.” Varga found the emotional shock of Brexit deeply upsetting at the time: “Our EU customers were our friends, but there was a sudden chill after 2016. My staff were upset when old customers said, ‘You bloody Brits! You’re ruining everything.’” His father, who founded the company, used to recall the joy of joining Europe in 1972. Once the CE came into effect, “overnight there was just one gold standard for every product exported to every European country instead of a plethora of kite marks”.

The Financial Times (FT) splashed this week with, “Business breathes sigh of relief after post-Brexit goods safety mark ditched”. But what a bitter “sigh” that is, says Varga. This sudden U-turn only became inevitable because the UK didn’t have the capacity to issue UKCA marks. Varga’s products are still waiting for a new product safety mark after a year. “The inspectors were overwhelmed.” Worse, his suppliers in the EU couldn’t get UKCA marks registered either, stuck in the backlog, with Britain demanding they be checked by a UK-domiciled body. Now he has to tell suppliers and customers they need never have bothered.

It has cost Varga tens of thousands of pounds just to provide the right records for his products. But Brexit has cost him £4m in turnover because of lost EU trade. He has been building up new trade worth £400,000 by reaching other markets. “The EU was and is our biggest market, but UK businesses have become persona non grata among many potential EU customers.” He yearns to return at least to the customs union, removing all import and export restrictions.

Unsurprisingly, the government U-turned a second time this week, yet again delaying imposing import tariffs on fresh food from the EU. Four times delayed already, the problem is that there are not enough inspectors and vets at the border, with long lorry queues bound for chaos. The unjust flat charge of £43 for every consignment, large or small, would raise food prices mid-cost of living crisis by £420m a year, says the FT. Brexit had already added nearly £6bn to food bills by the end of 2021.

A new model “will be published shortly”, but few expect this to happen any time soon. The food industry sighs with relief, except for farmers, angered at paying EU tariffs to export into the EU, with no reciprocal cost to EU farmers selling food here. The government spent £1bn preparing for inbound checks, but will they ever happen? Here’s the catch: outside the EU, the World Trade Organization will clamp down if Britain discriminates in favour of EU food imports against other countries.

Brexit damage isn’t a one-off, a hiccup, but ongoing self-harm; the Office for Budget Responsibility says it permanently diminishes UK growth by an extra 4%. On and on the damage goes, as we remain last in the G7 for growth. Heedless, the government pushed through its retained EU law act, allowing ministers to scrap thousands of regulations at the whim of a statutory instrument. Yet, retreat from a British-only product safety mark shows the practical and political futility of diverging from our biggest market on anything – employment laws, green laws, environmental protections, food or any other health and safety rules: voters won’t tolerate lower standards, so it’s not going to happen. The end of the UKCA signals that divergence is a dead duck, so there’s nothing left for Brexiters to cling to: control and sovereignty are lost with no say in setting our regulations. The total EU-UK goods trade had fallen by almost a fifth by the end of last year.

As Michael Heseltine’s European Movement keeps saying, there was no need for this hard Brexit, no need to leave education and research programmes Erasmus and Horizon, no need to reject EU overtures on defence and security cooperation. Suella Braverman’s immigration laws imperil EU cooperation on DNA, fingerprint and criminal records. On visas, the government is paralysed by the bad ideas of its Brexiters calling for fewer not more carers’ visas, and fewer not more of the foreign students who keep UK universities afloat.

Varga blasts the “car crash” imposed on his and all other exporting companies: they all warned the government against this rock-hard Brexit. It shows that Boris Johnson really did speak for his Brexit-delirious party when he said “fuck business” – and that went for all the rest of us too.

• This article was amended on 7 August 2023. An earlier version said that total trade had fallen by almost a fifth since Brexit to the end of last year; this should have said the total EU-UK goods trade.

• Polly Toynbee is a Guardian columnist