How do you solve a problem like Korea? It’s now 10 years since the American musical troupe Capitol Steps released their song of this name, a satire on the fact that it was a question which had everyone stumped. It’s a duet, where exasperated Americans ask Kim Jong-il “Why do you have to poke us with a stick?” He has a different question: “How bad do I have to be/to get you to come for me?” Their reply: “Well if you had oil, that might do the trick.” This summed it up: North Korea might be a monstrous regime, but it was a problem that the West could probably afford to ignore.

It’s getting harder to ignore now. Since Kim Jong-un succeeded his father six years ago, he has made striking progress with a weapons programme that’s designed to provoke America. Last year alone, he managed 24 missile tests and two nuclear tests – as if to provoke Barack Obama into a response. It failed. Last month, Kim tested a missile that he says was capable of reaching the American mainland. Earlier this week, he promised to fit it with a nuclear warhead. Then he finally got the reaction he wanted, as Donald Trump promised to unleash “fire” and “fury like the world has never seen”.