The classic conundrum “What happens when an irresistible force meets an immovable object?” can be applied to Brexit, and indeed to President Trump’s stand-off with the United States Congress over his pet Mexican wall project. His claim to be in possession of an irresistible force derives from his pledge to build a wall to keep out undesirables from the south, which was undoubtedly a popular factor in his election victory.

Theresa May’s supposedly irresistible force is the 2016 referendum result in favour of leaving the European Union. Her trouble is that too many politicians are immovably opposed to her way of honouring it – her controversial “deal” with the EU – and some reject the whole idea. In any event, a democracy that cannot change its mind ceases to be a democracy, as David Davis, the prominent Conservative Brexiteer, said in 2012.

In the American case, the White House insists “the will of the people” must be respected, and legislators must provide the necessary funds. They reply, inevitably, that part of Mr Trump’s pitch for the wall was that Mexico would pay for it, not the US taxpayer. In which case, the allegedly irresistible force becomes the will of the president rather than that of the people.