Boris Johnson’s supporters will always tell you he is hugely popular in the US, so the spectacle of the former British prime minister addressing a ballroomful of empty chairs at the Republican national convention in Milwaukee is hideously poignant. Politically speaking, it is obviously even worse than when Cheryl got binned off the US X Factor. The idea of one or other of The Anecdotes falling with no one to hear it … well, Johnson was not so much casting his pearls before swine as spaffing them all over an empty pigsty. But the erstwhile PM was not alone. I...