“Conservatives,” wrote the historian Robert Eccleshall, “are by temperament cautious and prudent”. Suspicious of grand schemes and utopias, they venerate “what works”, pride themselves on the practicality of their politics and remain sceptical of all theories and abstractions.

The through-line that links the ideologies of Burke, Disraeli and Thatcher is not simply that the state should be small, but that its administrators should by preference do little. For conservatives there is a natural order in society that, left to its own devices, tends to work fine.

That’s the theory. So I wonder what political historians will make of Theresa May.

The Prime Minister is, as I write, issuing instructions to deploy what’s left of the army onto the streets, come March, to clear special lanes for the motorcycle couriers who will zip around Britain with what’s left of our food and medical supplies.

Having designed an Armageddon project to scare parliament into backing her atrocious Brexit deal, she is now preparing to actually trigger no-deal. If it’s not real to you now, then the moment the government tells you not to book a summer holiday, voiding your insurance if you do so and obliterating hundreds of small travel firms, it will become real then.

British Conservatism, in short, has become incautious, imprudent and impractical. In pursuit of a grand scheme, it is preparing to plunge the economy into chaos and destroy itself as a party. Faced with something that actually did work (although not well), it is determined to destroy it in favour of an abstraction.

This prompts the question conservative thought is not well-equipped to answer: why? Conservative political philosophers tend to root justifications for their ideology in human nature, national characteristics, alignment to venerable institutions , or even in evolutionary neuroscience (in the primordial jungle, prudent humans survived).

When they consider class, they tend to assume that income inequality is both inevitable and (within limits) just, but that class categories and class dynamics are not a fit subject for discourse.

But to understand the glorious fiasco May has unleashed we must begin with class. The Conservative Party is supposed to be the primary tool for Britain’s business class to govern in conditions of democracy. That’s the real through-line – and what explains Toryism’s dominance after 1832 and its suppleness during the 20th century.

Its task in the 19th century was to strip away obstacles to what Peel called the “real economy”, while steering the middle classes away from radical democracy. In Toryism’s obsessive battle with abstractions, the abstractions to be avoided were usually those that might translate the principles of political democracy into economic democracy, or civil justice into social justice for the working class.

In the 20th century its task was to manage the interests of a bourgeoisie that had grown rich not just from industry but from empire and finance. Even when it had to manage the relative decline of all three, it did so without becoming particularly unhinged. So even though Macmillan and Thatcher stand at the polar opposites of post-war conservatism, you can still recognise what Michael Oakeshott called the “conservative disposition” running through their thinking like words through a stick of rock.

What’s gone wrong with Conservatism mirrors what’s gone wrong with the British bourgeoisie. After 30 years of globalisation it has become unanchored, fragmented and culturally detached from most of the institutions it was aligned to. When you meet rich people, say for example, the front 15 rows in the stalls at Covent Garden on a big Wagner night, the predominant flavours are the City, the boardroom, the elite universities, and the administrative class – civil servants, public affairs consultants and the odd politician.

If these interbred tribes - of finance, entrepreneurship and public administration - actually constituted a bourgeoisie, Conservatism would be alright. But there are really two Cities of London: the city of the light blue tie and erect bearing, which regards Mohammed bin Salman as a rotter, and the city of the dweeby technocrats who manage the money of crooks and dictators with obsequious enthusiasm.

And there are, in parallel, two intellectual spheres: one where rationalism and scepticism are prized and one where crazed, utopian, right-wing irrationalism is celebrated.

And since Blair, there have been two forms of statecraft: one suited to running a sovereign country with stable institutions, and another best suited to running government departments as outsourced businesses, prey to the influence of any foreign intelligence service that knows how to pull the strings.

These factions – the hedge funder, the property speculator, the best-selling irrationalist and the outsourcing civil servant – have constituted themselves into a kind of alt-bourgeoisie, which has no use for the conservative disposition.

Instead of constituting the top layer of a British hierarchy, the alt-bourgeoisie have formed themselves into the local branch of a global one, and turned London into the venue for all the dodgy money and practices needed to run their alt-capitalism, based on financial speculation and rent-seeking.

The problem is, we also have an upper middle class, which has to live in a real economy and polity. I meet them professionally every day: the pension fund manager, the accountant, the manager of a fashion brand, the sculptor, the hospital manager, the university lecturer.

What do they always say? “Politics is shit. No party represents me.” The economy’s stagnant and the political institutions of the country command no respect. Jeremy Corbyn and Vince Cable leave them cold. They tend to like Nicola Sturgeon but if they don’t live in Scotland that does not solve their problem.

Traditional, prudent, liberal conservatism would solve their problem but it no longer runs the Conservative Party. You can’t simultaneously represent the interests of a globally-focused, rent-seeking and utterly callous bunch of crooks at the same time as the upper middle class of a civilised country.

Brexit was always the project of the alt-bourgeoisie: not just in their desire to align with Trump’s pole in a multipolar world, or in the fantasy of reconstructing a white, English-speaking, trading empire. Above all what their businesses thrive amid is chaos. You can always trade unpredictability in the markets and, as the world goes down the pan, the price of a duplex apartment at Vauxhall Bridge will always go up.

And as the negotiations have faltered, and the possibility of a collapse scenario comes into view, Brexit has become precisely the kind of abstraction and utopia that conservatism is supposed to eschew. The mindset of the European Research Group, and the ex-Ukip members pouring into local Conservative associations, starkly resembles the Jacobinism that Burke decried in 1790.

Meanwhile, those who still believe in conservatism as a form of moderation – Amber Rudd, David Gauke, Oliver Letwin – do not know what to do. Rudd keeps making pronouncements out of a “book of good ideas” – an indicative vote, a second referendum, maybe a prime minister called Amber Rudd – but she cannot act on them because the Conservative Party is no longer really conservative.

The tragedy is that these factional divisions at the top reflect real ideological and demographic fractures across British society. The xenophobia and hubris of Tory right MPs is actually moderate compared to the rhetoric you hear in Wetherspoons: “we’re a great county, screw Europe, let’s go it alone; sod the migrants, I’d rather have them gone even if the economy does collapse – but we’re British, we’ll get by.”

When conservatism was aligned to a stable system, such bar stool irrationalism didn’t matter. You mobilised it for expeditionary warfare, you ignored it while organising a 21-gun salute for the Saudi monarchy. Now, the xenophobic tail is wagging the dog. Calling the shots are the kind of people who used to be shunned by real conservatives: the offshore investor with a penchant for all things Russian, the think tanks flush with money from American billionaires who want to smash the state.

We will probably remember 2018 as the year British conservatism began to fall apart. I don’t give a toss about the Tory party: it destroyed the society I grew up in and inflicted organised economic cruelty on entire regions of the country. But I do care about cancer patients getting their morphine on time, and about food being available for the microwaves of stressed-out mums, and about motorways being roads, not lorry parks.

Edmund Burke once wrote: “What is the use of discussing a man's abstract right to food or to medicine? The question is upon the method of procuring and administering them.” Early next year, for the sake of an abstraction, procuring food and medicine will become an all too concrete problem for May’s regime of crisis.

For this reason, I urge the real conservatives in the Conservative Party to use the Christmas break wisely - and get a grip.