Whodunnit? More whodunwhat?

I RELISH watching an Agatha Christie mystery on the telly; the intellectual challenge it poses is good for the brain. I’m not that big on trying to work out whodunnit, though, even if The Herald yesterday gave us the formula: apparently the killer will be introduced within the first half of the book on which it was based, and is likely to be emotionally involved with the victim. If there are a lot of land vehicles in the story, the killer is most likely female, and if there is a plentiful supply of nautical vehicles and aircraft, the culprit is most likely male.

This is all well and good, but it’s not much help to the TV viewer. It presupposes that a) you’ve read the book, and b) the writers haven’t played fast and loose with the story. Hardly ever do both a) and b) apply.

I rarely get to concentrate on the plot anyway; I’m too busy trying to figure out why the face of one of the supporting characters is so familiar. What the heck was he/she in before? Not so much a whodunnit as a whodunwhat.

The thing about the Marples and Poirots is that they are chock-a-block with jobbing actors. There’s always someone who’s vaguely familiar, causing you to rack your brains trying to work out where you saw them before*. And don’t watch Midsomer Murders or Casualty if you value your peace of mind.

The art of thespian spotting can be turned into a harmless household game: the first person to correctly identify what the vicar’s niece or the inspector’s dim-witted sidekick was in previously gets a cuppa made for them. Mrs A is annoyingly good at this; my tea-brewing skills have consequently been honed to perfection.

It goes without saying, I trust, that Googling on your mobile is beyond the pale. Mental dexterity and assiduous memory training are required here. I fit in some revision by flicking over to ITV3 now and again, where there’s always a Morse, an Inspector Frost or a Foyle’s War showing; this is the equivalent of a driving range for golfers.

I’m pleased to report that I pulled off a memorable triumph on Sunday night. The husband, Joe (Tom Goodman-Hill) on Channel 4’s Humans had been eluding us for weeks. Finally, it came to me: he was in series one, episode two of Spooks.

I would like to claim a black belt in TV geekery; but the more prosaic truth is we watched it on Netflix not so long ago. Still, never has a cup of tea tasted so sweet.

‘‘ I’m too busy trying to figure out why the face of one of the supporting characters is so familiar

* Una Stubbs doesn’t count. She’s in everything.