Over the years, Donald Trump has considered all sorts of melodramatic solutions to what he perceives is an immigration crisis in the USA: mass deportations, an alligator-filled moat, an electrified wall. It turns out all he had to do was win another presidential election and wait. Because if even half the number of liberal celebrities who’ve claimed they’ll flee to seek refuge abroad really do go, net migration should be balanced in no time. Call it The Donald Dash, The Trump Jump or the Maga Stagger, but report after report emerging from the other side of the Atlantic suggests the...