Did Churchill ever break into applause at the sight of Stalin, or JFK give a little ovation for Khrushchev? I suspect not. So it was striking to see Donald Trump’s thrilled reaction as Vladimir Putin approached him in Alaska last week. Some online cynics joked that it was natural that the American leader clapped: it’s not every day you get to meet your hero. Too strong? Perhaps. But Mr Trump has shown an abiding affection for the Russian autocrat. As our Lexington columnist notes, the American first praised Russia’s leader on television back in 2007 and has been a steady admirer since. Lexington unpacks the real collusion between the two men.

My hunch about their relationship: Mr Trump is drawn to anyone who exudes an aura of strength. Talk of morality, rules, duty or strategy bores him. He yearns, instead, to strike bold and quick deals with tough guys and to win prizes and adoration as a result. That makes for an unstable world.