Is there a surer sign that a middle-aged man has morphed into a fogey than the sight of him shouting at the television? Sunday evening is when my inner Victor Meldrew tends to be unleashed. Period costume drama is the proximate cause. The BBC usually, but not always, the culprit.

These shows – Poldark, Call the Midwife, Lark Rise to Candleford – promise a gentle drawing down of the weekend, a televisual duvet in which to wrap ourselves and banish thoughts of Monday morning.

The dramatisation of Len Deighton’s counterfactual novel SS-GB is the latest series to render me choleric. That’s in spite of the fact that there’s much to admire. Leading man Sam Riley is terrific as Inspector Archer, a wartime British detective trying not to be a collaborator. The plot, based on the idea that Germany had won the Battle of Britain, makes us wonder what we would have done. As a study in temptation, it is Lenten fare.

The devil, however, is in the detail. It doesn’t take much for the suspension of my disbelief to be suspended. The sight of Sam Riley’s hair is enough. The style worked perfectly when Riley played a troubled 1970s singer in the biopic of doomed Joy Division frontman Ian Curtis. But a 1940s copper? In the ultimate story of historical revisionism, it is Brylcreem that has been airbrushed from history.

Spotting historical inaccuracies in TV costume drama has become a national parlour game. Such is the hue and cry generated that I wonder whether it’s sometimes done knowingly by publicity-hungry producers. “If Ross Poldark swings his scythe up and down, not right to left, the Daily Mail’s bound to notice – let’s do it!”

My friend Alastair Bruce dismisses such PR fantasies. He is an expert in heraldry, a successful author and Territorial Army colonel. He’s also a royal and constitutional commentator used by Sky News, which is where we met. In recent years he’s carved out a niche as the historical adviser on films such as the Oscar-winning The King’s Speech. I’ve been his guest on the set of Downton Abbey, whose producers he helped avoid anachronisms for five years.

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