They have period names in the foreign country we call the past. In last night’s documentary about a brilliant wartime trick practised upon Hitler, we came across a coroner called Sir Bentley Purchase, a love interest called Peternel Hankins and a Welsh tramp with the stirringly patriotic if implausible name of Glyndwr Michael. Charles Cholmondeley, one of the authors of the deception, would even draw attention to the absurd discrepancy between the way his name looked and sounded. More or less the only person in this entire story who didn't sound like a character in a novel was Major Bill Martin, and yet he was entirely fictional. How on earth did the Nazis not smell a rat?