David Mitchell is as brilliantly awkward as ever as a puzzle setter who poses as his twin in order to find out why his brother has disappeared. It’s enjoyably gentle case-of-the-week TV

Imagine if Mark Corrigan from Peep Show grew up, shucked off Jez and Croydon and became a puzzle setter living a quiet life. Not hard, is it? But it wouldn’t make for much of a show, so let’s give him a twin brother who is a police detective who goes missing while secretly investigating a case he has told his wife nothing about, yes?

That is the premise of Ludwig, in which David Mitchell plays an older Mark-type character – this one is called John – whose semi-estranged sister-in-law, Lucy (Anna Maxwell Martin), calls him out of the blue to tell him she needs him to come over. There is a taxi waiting outside for him, the spare bed has been made up – with three pillows, no less – and Lucy will make whatever pasta he had planned for his supper when he gets there. As ever when Mark (now John) is involved, I – and perhaps I can speak for all my fellow pedant-troverts here – feel very seen.