It’s elementary! Meet your new supersleuth . . . Miss Mel Marple

Sue Perkins has hit by accident on a whole new format for a detective series. Give her old Bake Off chum Mel Giedroyc a box of family photos and let her go to work.

she’s a natural sleuth, a Mel Marple. seizing a picture from the wedding of sue’s parents, on Who Do You Think You Are? (BBC1), she ignored the happy couple and focused on their mothers instead.

Mel wove theories about their personalities, based on their hairstyles and their body language, that proved remarkably insightful.

And she pointed out clues, such as an address embossed in tiny print on the frame, before becoming emotional over a letter hidden among the photos.

in short, she took over, and it’s a pity sue didn’t bring her along as she traced her ancestors, from Bodmin in Cornwall, to a ploughed and frozen field in Lithuania.

While Mel got tearful, sue was constantly cross. We first saw her in a boxing gym, letting off steam by pummelling pads held up by her sparring partner.

so much about her family’s history made her boiling mad. in particular, she was furious that during World War i her mother’s grandfather emil Muller was interned for the duration.

A tailor in the east end of

London, emil was arrested with thousands of other German-born Brits and sent off to a military camp on the isle of Man, effectively a prisoner-of-war.

i suspect sue secretly blamed Brexit. she seemed to forget that millions of British troops were fighting to hold back the kaiser’s armies and that, with the constant threat of invasion, German spies were a very real problem.

Oddly, she had a chuckle at family legends about her grandfather, Albert, a professional soldier who was barely 5ft 6in: he was safe in the trenches, she said, because the bullets flew over his head.

Albert survived the slaughter in the Dardanelles, before being invalided home with trench foot, a crippling disease. i can’t quite understand the viewpoint that shrugs off his ordeal, yet seethes at the wartime bureaucrats who segregated foreign nationals.

This is where Mel’s intuitive talent could have made the episode much better. someone needed to

explain to sue that imposing your own outlook on the past, and expecting your ancestors to be treated according to 21st-century norms, is small-minded.

Future editions promise to be less frustrating. The research is so thorough, and the stories are revealed with such skill, that major celebs line up to appear.

in this series, richard Osman, Matt Lucas, Anna Maxwell Martin and ralf Little are among guests hoping to discover royal ancestry and war heroes.

The chief frustration of PRU (BBC3), a sitcom set in a ‘pupil referral unit’, or school for impossible teens, was that most of the dialogue was incomprehensible.

Thick with slang and slurred through exaggerated adolescent mumbles, half the lines were lost. Actors playing the teenagers are all in their 20s. echoes of Harry enfield and kathy Burke as kevin and Perry.

When they could be decoded, the quips were unimaginative. One girl, sienna (nkechi simms), excused her friend’s behaviour: ‘it’s all right, miss, he ain’t taken

his meds. not his fault, he’s got that ABCD thing, innit.’

The running joke was that pupils were so fed up with hyperactive Halil (Jaye ersavas) that they dosed him with his own ADHD medication. When, under the influence, he tried to steal a teacher’s car, they all owned up.

This is the sort of comedy where ‘valuable lessons are learned’, like a preachy remake of Grange Hill.

HHIII