When a run of bad luck is gathering momentum, sometimes the instinct is to gamble what’s left in a do-or-die gesture. That explains Rishi Sunak’s behaviour on May 22. He could limp towards oblivion, with dissent festering among voters and a continuing trickle of defections from his Conservative Party to Labour. Or he could surprise friends and foes by calling a snap election for July 4. John Donnellan’s put-down of Alan Dukes – “If it was raining soup, he would be out with a fork” – came to mind when Sunak announced his bold decision. The rain poured down on…