Gimson’s Prime Ministers, out this week, is a crisp and stylish account of every one of them. I happened to be reading Andrew Gimson’s admiring essay on George Canning (PM for 119 days in 1827) just after Jeremy Corbyn’s parliamentary remarks about the Salisbury poisoning. The way Mr Corbyn talked, one got the impression that it was Britain which had caused Mr and Miss Skripal to be poisoned. Canning had a gift for light verse. He satirised the sort of Englishman who adored the French Revolution: ‘A steady patriot of the world alone,/ The friend of every country but his own.’ That Phrygian cap fits Mr Corbyn perfectly. It is constantly, patronisingly said that young people don’t care about Mr Corbyn’s consistent support for terrorists, dictators and revolutionaries over 40 years, and it may be true that some of them have been so badly educated that they do not know much about the West’s struggles against totalitarianism. But this story is the key to understanding Mr Corbyn, and therefore it needs to be told as urgently as possible — to prevent him featuring in later editions of Gimson’s work.