Five Go Mouth-swabbing is a terrible twist to a well-loved classic

Dr Mandy Hartley, a forensic scientist turned children’s author, made waves at the Cheltenham Science Festival this week. Updating classic tales to include DNA testing, she suggested, would engage young people in forensics. Though usually armed with little more than a picnic lunch and their own ingenuity, Hartley claims Enid Blyton’s Famous Five could have solved their mysteries faster by trading in their flimsy pocket maps for chromosome mapping. (What’s next, Five Go Mouth Swabbing?)

While this might be a brilliant way of raising awareness of forensic science, it risks doing to children’s literature what has already happened to adult detective fiction since the advent of DNA testing, iphones and CCTV – taking all the fun out of it. Today, almost every crime drama seems to hinge on DNA evidence, rendering the deductive methods favoured by the likes of Sherlock Holmes, Hercule Poirot and Miss Marple completely obsolete.

In The Hound of the Baskervilles, Holmes ingeniously sheds light on a sender of threatening letters, made from newspaper cuttings (sadly, not this one). “The address, you observe, is printed in rough characters. But The Times is a paper... seldom found in any but the hands of the highly educated. We may take it that the letter was composed by an educated man who wished to pose as an uneducated one.” Nowadays, a quick Google search would allow Holmes to cross-check numerous typefaces on the spot – if the sender had avoided leaving DNA traces.

Raymond Chandler once dismissed Agatha Christie’s focus on seemingly minor details as “futzing around with timetables and bits of charred paper”. Yet therein lies the genius of both Christie and Conan Doyle – the snapping up

of unconsidered trifles.

These days, our ubiquitous CCTV cameras would unmask Poirot’s ABC murderer, while DNA testing would rapidly unravel one major clue in Death on the Nile, a single letter scrawled in blood at the crime scene. The many plots relying on mistaken identity would dissolve within minutes. Murder on the Orient Express might still out-fox the authorities today; the DNA of multiple suspects would litter the crime scene, possibly compromising it; though this, too, could lead investigators to draw the same conclusion as Poirot.

The genre suffers when deduction is discarded, and writers overcompensate with implausible storylines and endless twists. ITV’S Midsomer Murders delights with its combination of light whimsy and improbable bloodbaths: John Nettles’s hapless DCI Tom Barnaby invariably discovers the killer only when every other suspect has been minced by a combine harvester or crushed by a giant cheese wheel. Line of Duty’s fast-paced episodes disguise gaping plot holes, character flaws and terrible inconsistencies.

The best mysteries provide ample evidence and time to assess it. A smart 11-year-old might be able to solve Conan Doyle’s peerless The Adventure of the Speckled Band – with a few hints from Mum or Dad – but the BBC’S modern iteration, Sherlock, doesn’t even try to bring the viewer along, too. We may marvel at the writer’s ingenuity, but any solutions remain well beyond our collective grasp.

Let’s hope the Famous Five stay well clear of the lab, in the great outdoors with their binoculars and ginger beer, where they belong.