The Foreign and Commonwealth Office is one of the most imposing buildings in Whitehall. An Italianate palazzo plastered with bombastic murals and dripping with more gilt than a footballer’s mansion, it is a subtlety-free zone which has since the 1860s been used to project Britain’s power and status. That unshakeable self-importance has traditionally been associated with those who work there too.

So it was telling, yesterday, to see the staff of the Foreign Office huddled together as if for safety beneath the soaring ceiling of the Grand Locarno Room, the grandiosity of their surroundings serving to highlight their vulnerability. Men and women, some so young they looked as if they were on work experience, listened nervously to the FCO’s chief Sir Simon McDonald as he sought to reassure them in the wake of the Kim Darroch affair. The image said: we’re circling the wagons because we can no longer trust our own Government to defend us.

We’re not talking about Theresa May and the Foreign Secretary Jeremy Hunt, who have both stood steadfastly by Sir Kim Darroch since telegrams were leaked revealing his disdain for President Trump’s White House, prompting the toddler-in-chief to throw the contents of his diaper at both Sir Kim and Mrs May.

But Mrs May’s is a ghost administration, stuck straightening the cushions in No 10. What Foreign Office officials fear is the incoming government of Prime Minister Boris Johnson.

If the Darroch incident tells us anything, it is two things: it confirms that Boris Johnson is happy to preside over the undermining of key institutions, in this case the civil service; and that Britain’s “independence” after Brexit is a tragic fiction. For all that Mr Johnson is willing to inflict untold damage on the UK economy by leaving without a deal in the name of “taking back control”, he seems ready, to borrow one of his own phrases, to edge Britain towards becoming a “vassal state” of the US instead.

Mr Johnson’s refusal to rule out sacking Sir Kim was the most abject moment of Tuesday night’s debate between the two Tory leadership candidates and its significance was what it said about his respect for the institutions of government. The right thing to do would have been to support the ambassador staying in office until his retirement at Christmas, not just out of loyalty to a long-standing public servant but to emphasise the UK’s absolute right to determine for itself who it appoints to key diplomatic roles and avoid setting the dangerous precedent that the United Kingdom could be pushed around. Instead Mr Johnson had “thrown this fantastic diplomat under the bus to serve his own personal interests”, as the furious Foreign Office minister Sir Alan Duncan put it. There can be very little doubt that this is what precipitated the ambassador’s resignation less than 24 hours later. It has badly shaken civil servants’ trust in politicians, leaving them in dread of being hung out to dry if their words are leaked.

If Mrs May appointed Sir Kim’s successor it would spike Mr Johnson’s guns. But if it is left to Mr Johnson, there is widespread speculation that he could go for a political figure who could be relied upon to cosy up to the Trump administration – Nigel Farage has been mooted – instead of the usual choice of an impartial career civil servant.

Should we be surprised by this latest unedifying episode in the Boris Johnson show? Not in the least. He has already demonstrated his cavalier attitude to the institutions that make up our democracy and government. The UK is a parliamentary democracy and the government derives its authority from MPs, yet Mr Johnson stands ready to padlock Parliament and leave MPs pounding their fists on the doors outside, in order to force through a no-deal Brexit against their will.

The irony of Brexiter fanatics around Mr Johnson seeking to return sovereignty to the British parliament by abolishing the British parliament, is testing the bounds of satire so severely that it’s giving newspaper cartoonists migraines. And there’s more (there’s always more): Mr Johnson’s team have now attacked the former Tory Prime Minister Sir John Major for wanting to “drag” the Queen into politics with his threat of a judicial review to stop prorogation, even though it is they who would be miring the Queen in all this, by advising her to shut down parliament against MPs’ wishes.

Read more: A Scottish Citizens Assembly is compromised – we should have a British one too

I know. Take a minute. Perhaps a glass of water would help, or better still, whisky. It’s madness.

But there is method in it, from their point of view. The hard right who now have the Tory Party firmly in their grip, are unabashed fans of Donald Trump. He represents, for them, a fellow spirit. They favour a deregulated, low-tax British economy which is hostile to immigrants, much as Mr Trump does. They care little, it seems, about the low-paid, insecure jobs such conditions engender. If they worry about the impact of a no-deal Brexit on public services, they have kept very quiet about it.

Their Holy Grail is a trade deal with the US. Such a deal is seen as the ultimate vindication for Brexiters, and the worry is that they will go to any lengths to secure one. Will Mr Johnson pander to Mr Trump’s demands that the NHS pay more for drugs? The US gripe is that the large, state-run NHS has a negotiating advantage over privately-run health providers in the fragmented American market. Can we trust that the NHS is sacred ground for Boris Johnson when parliament and the civil service are not?

As for foreign policy, with the US and Iran at risk of blundering into an accidental war, how far will Mr Johnson go to avoid upsetting the Donald? He has abandoned an ambassador who spoke truth to power; would he be willing to do so himself? Those are the real and alarming questions now facing us as the handover of power at No 10 approaches.

It is years now, thankfully, since the so-called “Scottish cringe” was a phrase in common use, describing the internalised lack of self-confidence that was said to afflict many Scots. But, incredibly, now we are seeing the beginnings of a British cringe, the head-in-hands embarrassment of having fanatical Brexiters and Trump sycophants on the threshold of Downing Street. Better have that whisky at the ready.