The return of the criminally overrated Sherlock should have come with an apology to everyone under the age of 40. You know, young people who couldn’t give a damn about that woman they’ve only vaguely heard of, Margaret Thatcher.

The writers, of course, are of a certain age. Of that generation that remains obsessed with the Tory Prime Minister who broke the unions and ignored the left-leaning metropolitan elite who go to university and then join the BBC. They can’t let Maggie go.

And so it was that we tuned into the The Six Thatchers, the endless New Year special throughout which we saw busts of the former premier being methodically smashed in waves of sledgehammer symbolism that were so unsubtle they were laughable.

That’s the trouble with Sherlock. It tries so hard to be dazzlingly clever but always ends up looking rather dim. Channelling their own self-styled brilliance through the thoroughly unlikeable eponymous hero, the creators get poor Benedict Cumberbatch to spew faux-genius gobbledegook at break-neck speed that’s impossible to follow and therefore truly annoying.

Horribly allergic to cogent story-telling, this puffed-up production took a straightforward tale and endeavoured to make it as confusing as possible. That master of story-telling Sir Arthur Conan Doyle – on whose detective novels this daft drama is extremely loosely based – must be spinning in his grave. He wrote whodunits. Now the burning question is: who ruined it?

Anyway, for what it’s worth, The Six Thatchers might have just about passed muster as a standard issue 60 minutes of mindless escapism. But stretched to an interminable film-length hour and a half, it died an agonising death. As did Dr Watson’s wife Mary who turned out have been part of a secret squad of freelance murderers. Gosh.

While Sherlock didn’t have time to dodge a slow-motion bullet, Mary mysteriously had time to jump in front of it and she passed away churning out clichés in her howling husband’s arms. I replayed Martin Freeman’s bizarre banshee cries of distress because they were so funny.

“You were my whole world,” sighed Mary with her last breath. Who came up with that humdinger of an original line? Walt Disney?

After her corny demise, it got worse. The proverbial pre-recorded video beginning with: “If you’re watching this I’m probably dead.” Really? Can’t they do better than that?

Despite the desperate attempts to complicate it, the puny plot was as simplistic as the asinine anti-Thatcher theme. In a case of mistaken identity it wasn’t Mary who betrayed her killer mates, it was some old secretary called Veronica Norbury.

“Veronica Norbury,” boomed the ever-modest Sherlock. “You outwitted them all. Except for Sherlock Holmes!” Oh, whoop di do, well done. Then Veronica gunned down Mary and weeping Watson told his self-congratulatory chum to go to hell.

At the height of this brainless nonsense, chief spook Lady Smallwood turned to Holmes’ toweringly irritating brother Mycroft and snarled: “This is absolutely ridiculous and you know it.” He wasn’t the only one. The viewers were onto it too.

Powerhouse production values, cracking cast, shame about the script. It all looks slick and, along with the strong team of support players, Cumberbatch and Freeman are very fine performers. But they’re like carpenters working with paper. The flimsy material’s all wrong.

Strangely enough, it ended in promising fashion. Humbled by his own tragic mistake, Sherlock at long last showed some humanity as he attempted to mend the bridges with the heartbroken Watson. It has always been impossible to warm to Sherlock, now we may finally be able to.

In another of her parting shots, Mary gasped: “Save John Watson, save him, save him.” Not exactly Shakespeare, but definitely intriguing.

And with the terrific Toby Jones set to join the fray as an epically evil villain, the next episode should be a vast improvement. It certainly can’t be any worse. Here’s a safe bet though: it won’t be called The Six Corbyns. Just fancy that.