Stewart Jackson was Chief of Staff to David Davis when he served as Secretary of State for Exiting the European Union. He was also MP for Peterborough from 2005 to 2017.

We are now at the denouement: the crossing of the Rubicon, Butch Cassidy and the Sundance Kid, the Alamo. However you cut it, Theresa May has run out of road. She’s more Wily Coyote on the cartoon clifftop. It won’t end well.

Incompetence and being accident-prone is one thing, but guile, subterfuge, undermining the basic tenets of Cabinet government, setting up a parallel governance structure peopled by true believers and sycophants, sidelining Parliament and selling out your solemn promises on, inter alia, leaving the Customs Union and removing the United Kingdom from the remit of the European Court of Justice, is something quite different, and invites scorn rather than sympathy.

Duplicity and mendacity has become a specialism in this administration: how can you nuance a capitulation on a long-held commitment to having no border in the Irish Sea, and then try to convince your party that gifting the province to Brussels as a colony, at least in respect of its regulatory regime, is fine and dandy? What message does this send to the Conservative Unionists in Scotland fighting the Scottish Nationalists’ demands for a similar deal?

A genuine attempt to make good her seemingly sincere pledges to strive for a comprehensive trade deal, with a consequent rebuff from the EU, would have elicited admiration from her own Party and the wider country for her plucky efforts. It would have consolidated her reputation for diligence, hard work and commitment to public service. It would have enabled most Conservative MPs to forget that she was elected not because she had any particular merit or talent, but because she was the last woman standing.

And then, of course, there is her abysmal performance as a “presidential” candidate at last year’s general election, and the lack of emotional intelligence that blew a 21 per cent poll lead in just seven weeks, and almost visited upon the UK the calamity of a Corbyn Government – and a Marxist Chancellor of the Exchequer in Number Eleven Downing Street.

There was good reason that, in the Conservative Whip’s Office, May was always seen as a “tricky” customer. Plus ca change.

What took place this summer was a carefully-planned establishment coup in the form of the Chequers fait accomplis, and a Cabinet meeting on 6th July which would have made old-style Communist despots blush. Ministers were bounced with less than a day’s notice by 120 pages of papers on the tenth iteration of a Brexit White Paper that few had seen, but which most assumed was based on the Prime Minister’s vision as enunciated at Lancaster House, Florence and Mansion House.

This was a reasonable assumption, since much of the detailed legal text of an ambitious trade deal based on “best in class” precedents from across the globe had already been written by officials in the Department for Exiting the European Union. Instead, Ministers’ phones were confiscated; there was childish briefing about Ministers taking a taxi home if they didn’t like the Prime Minister’s plan, and a communique was issued in their names before they had even seen it – all part of an “iterative process”, apparently. Meanwhile, pro-Brexit Ministers were dangled undertakings of promotions at the same time as their current jobs were being offered to others to keep them on board. What a way to run a Government!

We saw all this sort of stuff during May’s reign at the Home Office. She is truly Nixonian in her modus operandi, with her two stalwarts in the Number Ten bunker, Robbie Gibb and Gavin Barwell, fulfilling the Bob Haldeman and John Erlichman roles. There is no trust of those outside the inner circle, disdain for Parliamentary scrutiny, misjudgement in the Whip’s Office and, most recently, an abject misreading of the Democratic Unionist Party, which will always put a premium on identity and history, no matter how much gold one tries to stuff their mouths with: where are Woodward and Bernstein?

I admit that we in DexEU should have seen it coming. There was a reason that Number Ten was desperate to prevent the publication of a White Paper before June’s EU Council. It was desperate to stop proper, timely No Deal planning; desperate to prevent the publication of a draft legal text on the Irish backstop – and desperate to halt the deployment of dozens of specialist technical negotiators on the UK side from heading to Brussels earlier this year. All that wasn’t part of the plan.

Which is: that we must remain in the Customs Union, and endure a kind of semi-skimmed faux Brexit, which mandarins and compliant Ministers can deliver as an alternative to the real McCoy which they hate with a passion.

Greg Clark’s account of his dealings with Nissan is dubious, of course, and he has failed to publish correspondence with the company despite pledging to do so to the Commons last November. Philip Hammond and Clark’s officials, plus wonks friendly to them, were briefing from January this year that the UK would be staying in the Customs Union, and that the Irish backstop was the cleverest possible wheeze to ensure that this happened. For them, it has always been all about following the diktat of the last CEO of a multinational company with integrated supply chains which sat on them.

The July Chequers ambush was actually the second strike. The Prime Minister and her Europe Adviser, Olly Robbins, tried a similar ambush at the earlier February Chequers meeting, only to be thwarted by Davis, who flushed out what they had planned and refused to play ball, causing them to back off by way of a tactical retreat.

In hindsight, it is clear that they then began planning to circumvent their own Secretary of State rather than deal with him openly. Davis had always doubted the efficacy of agreeing the Irish backstop, and told the Prime Minister so in December 2017 and again in May this year, when he managed to extract from her a pledge to seek a definitive date for the backstop protocol to expire. Number Ten reacted by briefing against him furiously.

The backstop has now become the issue at the core of May’s latest and last stand. How could it not be? It should never have been allowed to develop mythical status. The UK should have never conceded its centrality in the sequencing of the Article 50 process. The problems it poses could have been satisfactorily resolved within weeks of the publication of the Government’s detailed technical papers in August last year. For at heart, the backstop is an issue not just of technical facilitations but of political good will, hitherto lacking in the EU Commission and the bombastic and aggressive virtue-signalling of the Irish Prime Minister and his deputy.

By locking the United Kingdom into a semi-permament customs union (which would be never-ending, since the EU operate on treaties and legal texts, and certainly not via “review procedures” or “gentleman’s agreements), we would gift the European Union the dream outcome for the project’s theological purists in Berlin.

We would be punished and hobbled as trade rivals. They would relieve us of north of £40 billion to leave, destroy our competitive advantage by effectively killing our prospect of future global trade deals, and keep us shackled to their rulebook and judicial oversight – in order to benefit their own commercial interests, and all whilst we have no say or influence. Ever again. Job done – thanks to May and her perverse mix of obduracy and fawning supplication.

Should she return from Brussels this week with a deal which egregiously betrays the referendum result, the Prime Minister will surely be removed from office – not least because she has so wilfully refused to engage with those seeking to save her premiership by imploring her to pivot to a Canada-style free trade deal. After a while, a gift horse is likely to give you a kick where it hurts.

In this event, she will thus be gone – either by way of a no confidence vote from her own party or after the defeat of a Withdrawal Agreement motion in the Commons. Her tenure will be over the moment a confidence motion is tabled by Graham Brady, because so many of her colleagues cannot risk her getting anywhere near the next election as leader. Her removal would be the start of a process of healing and finally, brutal though it might be, an end to the Tory Europsychodrama.

For all that, it rests with her alone how painful the defenstration will be – and over what timescale. Her historic legacy may be that she did her best and bailed out at the right time. Or that her stubborness and vanity tipped the Conservative Party out of power after a vicious civil war, paving the way for the most extreme left-wing regime in our history to assume power.

Only May can make that choice in this the loneliest job at the bleakest juncture.