The case for Brexit rested largely upon two misapprehensions – or, to put it less kindly, lies. The first was the belief that engaging in a deep and broad partnership, with the necessary compromises and disadvantages that brings alongside all its benefits, was an act of treacherous self-sabotage. The second was a wholly unrealistic assessment of Britain’s international status and heft, rooted in a vague, nostalgic vision of its imperial past. A third myth sprang from these two: that a post-Brexit Britannia would emerge triumphant, a beacon of democracy, parliamentary sovereignty and prosperity, shining across the waves.

The last three years have left such ideas in tatters; the last week has ripped the remaining shreds away. Its events have left Britain appearing not only backwards-looking, irrational and divided, but fanatical, bitter, frivolous, chaotic and heedless of any legal or customary impediment to the executive. Boris Johnson promised a stroll to sunlit meadows; now he offers a grim, hellish march towards no deal, and his troops have had enough.

The most damning attacks come from within: from his MPs, and now his ministers. Amber Rudd ditched her opposition to no deal as Mr Johnson ascended the throne; now she has quit the cabinet and the Conservative whip, accusing him of an assault on “decency and democracy” for his purge of Tory veterans. In interviews she pressed home her attack, noting that legal advice on prorogation had not been given to the cabinet despite repeated requests and that there is no evidence that the government is seeking a deal, since it is devoting 80% to 90% of its time to planning for no deal.

Days before, Jo Johnson quit, citing a conflict between family loyalty and the national interest. Kenneth Clarke, ejected from the Tory benches after almost half a century, warned that a no-deal Brexit could be far more damaging to Britain’s economy than a Corbyn government. As briefings from Downing Street grew wilder, the lord chancellor felt obliged to announce that he would abide by the rule of law and had spoken to the prime minister about its importance.

Consider now the external view. The EU diplomats with whom we will have to work, with or without a deal, are ever more frustrated by the game-playing and have accused the prime minister of reneging on pledges to uphold the Good Friday agreement. (The taoiseach, who will on Monday meet Mr Johnson, has already warned that he does not expect any breakthroughs.)

But other parties are just as scathing. In his Radio 4 series As Others See Us, Neil MacGregor noted that respect for Britain’s parliamentary democracy and steady pragmatism are much diminished, and that the world sees an unsettled nation cut adrift from its moorings. One American columnist dubbed this week Britain’s stupidest hour, while Canada’s Globe and Mail, describing the appetite for national self-destruction, observed that the Tories had transformed themselves into a protest party “even while continuing to govern a Group of Seven nation with a permanent seat on the United Nations security council”. Implicit in that statement was a question: how long, in these circumstances, can we maintain this standing and hang on to these levers?

That the Trump administration cheers Britain towards the exit, as Vice-President Mike Pence did again in London this week, is a cause for concern, not reassurance. It wants to speed our course not from its deep amity towards the UK, but its deep hostility towards the EU. Any opportunity to undermine European cohesion, weakening it in global trade and diplomacy (notably vis-a-vis Iran), is welcome. A trade deal with Britain, inevitably on terms highly favourable to America, will merely be the glaze on the chlorinated chicken.

With friends like these, who needs to make more enemies? To say that Britain’s hard power has long been in decline is merely an expression of the obvious, not of doomsaying. Now the Brexiters who dreamed of restoring glory are daily eroding the soft power it amassed as its empire shrank. Those who doubted our goodwill and good intentions after the 2016 vote increasingly doubt our good sense too.