The task of Whitehall’s National Security Council is to map the threats facing Britain. It has plenty of material to work with: Islamist terrorism, Russian revanchism, the Middle East in flames, rising nationalism, nuclear proliferation and Chinese cyber attacks among them. The other day, though, the council’s senior min-isters and policymakers took a different tack. What if the biggest danger turned out to be hiding in plain sight?

The question posed — and, as I understand it, not fully answered — at this particular meeting was whether the strategic challenge lay not so much in the intentions of known adversaries, but in those of Britain’s most vital ally. For 70 years the cherished special relationship with Washington has been a pillar of British foreign policy. But for how much longer will the US be a dependable ally?

Reading the latest headlines you can see why Theresa May’s government might have doubts. The prime minister is fighting for her political life to win parliamentary support for the Brexit deal she has struck with the EU27. US president Donald Trump’s response to her predicament was the casually wounding judgment that Brussels seemed to have called all the shots and may well have thwarted a bilateral trade accord between Britain and the US. With friends like that?.?.?.