THICK as mince, lazy as a toad, vain as a narcissus – as a collision of mixed metaphors (or rather similes) that assessment of the qualities of the Brexit Secretary, David Davis, takes some beating. It was tweeted by one Dominic Cummings, former director of Vote Leave and acolyte to the Environment Secretary, Michael Gove.

Having watched Mr Davis’s career to date, the underlying assessment seems sound. Yet, he is now in sole charge of the most complex, multifaceted and constitutionally momentous negotiations Britain has conducted, certainly since the Second World War.

Mr Gove also came in for a rhetorical mugging by an unnamed cabinet minister who suggested that he, and his comrade in calamity, the foreign secretary, Boris Johnson, were “donkeys” in need of being put down. “Too much testosterone” said the source, widely believed to be Home Secretary Amber Rudd, “from safe seat kids”. Phillip Hammond, the Chancellor, is trying to f *** up Brexit, according to another cabinet minister, because he believes the Brexiters are a bunch of “smarmy pirates”.

It’s about time Theresa May put a bit of stick about, said the Tory backbench 1922 Committee. But the trouble is that Mrs May is in no position to engage in cabinet purges right now, not least because it might end up with her being tossed inadvertently on the scrap-heap. The calls for her to “show who’s boss” by chopping off a few ministerial heads would only make sense if she really were in charge of events, which she manifestly is not. Shows of strength by weak political leaders rarely work because the purged ministers have nothing to lose, and can freely expose the follies and failures of the prime ministers who wielded the knife.

The prosecco-fuelled end of term acrimony in the Tory camp this summer has largely eclipsed the bitter rivalries in the Labour Party over the past two years. It’s possible of course that things could stabilise for Mrs May – there is, after all, no alternative, as one of her predecessors said in a different context. No one in the Tory Party wants a leadership election in case one of the donkeys or the toads ends up in Number 10. And there’s an understandable fear of another early General Election after the June disaster, when Mrs May threw away a 20-point lead in an election she thought she couldn’t lose. Suddenly Tory MPs are saying how wise the Fixed Term Parliament Act is.

But stay or go, boss or not, Mrs May is a deeply troubled figure in charge of a Conservative Party that has become raddled by the lurid passions unleashed by Brexit. Indeed, the Conservative cabinet resembles a bunch of blue Trotskyites, with their impossibilist demands, their ideological fantasies and their splits and divisions. Tories have discovered the language of internecine dissent, and found that they’re rather good at it.

It leaves the rest of the country in the position of horrified onlookers to a ministerial rammy that would be funny if it weren’t so serious. The Government has been in disarray for more than a year now, and it has become steadily worse as the Brexit clock has started ticking. Mr Davis walked out of this week’s round of talks with the EU negotiator Michel Barnier after an hour. I don’t know which is worse: that he bowed out before anything serious was discussed, or the explanation given by spokespeople that no one expected him to stay any longer.

The attitude of ministers like Mr Davis, as reflected in the house journal, the Daily Telegraph, is that the EU are all boring lawyers who love to bury negotiations in thickets of irrelevant legal detail.

The way to deal with these speccy types, with their piles of paper, is to wave it all away and stick to a few basic British principles. Such as: “Brexit means Brexit”, “have cake and eat it”, “no deal better than a bad deal”, “they need us more than we need them” and when it comes to paying the divorce bill “they can whistle for it”.

The stupidity of this approach has been outlined repeatedly, not least by the University of Sussex report on agricultural this week. Food security has not been an issue in Britain for at least 50 years, but that is largely because it has been handled at the European level – not just by the bureaucrats, but by the revolution in logistics.

Fruit and vegetables are constantly on the move across Europe’s 500 million consumers, the inventory contained in those massive lorries that thunder up and down the motorways. The report laments that no thought has been given to what happens when Brexit creates a huge logistical bottleneck at Dover, where 10,000 freight lorries pass every day. Food is only one of the complex supply chains that cover Europe in a dense network of integrated production.

The blinkered jingoism of the Brexiters, with their aversion to detail, has prevented them realising that the EU is actually offering a solution to this problem; to save them from themselves, as Tony Blair and Michael Heseltine have pointed out.

You can read about the compromise in a report from the influential Breughel Institute. Europe After Brexit. This proposes that the UK should remain, like Norway, a part of this complex integration of goods, services, capital and labour – but with an important caveat. While there is an assumption of free movement of labour, this would not mean “unrestricted movement of people”.

It is pretty obvious that Europe is moving in this direction already, not least because of the refugee crisis. While some countries like Germany remain committed to open borders, others, like Denmark and Sweden, have been shutting the doors very forcefully in migrant faces. Border posts are going up all over Europe, and there never has been any obligation on Britain to join the Schengen free passport zone.

This really would be a case of having their cake and eating it. Britain would leave the EU, the CAP, and the jurisdiction of the European Court, except for narrow trading issues. If the Brexit ministers had half a brain they’d seize on this and claim, not only that they have saved Britain’s economic security, not only that they have taken back control of borders, but also that they’ve forced Europe to change its ways.