Get the biggest stories sent straight to your inbox Sign up for regular updates and breaking news from WalesOnline Thank you for subscribing We have more newsletters Show me See our privacy notice Invalid Email

SHERLOCK came home to Cardiff this week. Not the kick-boxing Robert Downey Junior version but in the super-cerebral and febrile form of Benedict Cumberbatch.

The actor who has propelled Conan Doyle’s sleuth into the 21st century, took part in a Q&A after a special Bafta Cymru preview screening of tomorrow night’s episode – an interpretation of the The Hound of the Baskervilles.

Cumberbatch was joined by Sherlock writer Stephen Moffat – who also pens Doctor Who – and co-star and co-writer Mark Gatiss, aka Holmes’ big brother Mycroft. The trio gave an absorbing insight into the cleverest programme on British television.

Made in Wales, it’s got it all. The bromance of Holmes and his wingman Watson, the latter portrayed with such fabulous subtlety by Martin Freeman. Brain-aching plots brilliantly modernised from the Conan Doyle source material. Blockbuster movie-standard editing. Laser-sharp scripts. A terrifying Moriarty. And the inspired casting of Una Stubbs as Mrs Hudson.

It’s also the first drama to understand the power of social media and incorporate it into its very fabric.

There’s no clunky add-on website ticking the “multi-platform” box. You can click on Watson’s real blog while the scandalous Irene Adler’s Twitter account was trending before the first episode had even finished. Sherlock knows it has an audience surgically attached to smartphones and connects directly with them through its on-screen textual intercourse.

It’s a relationship which has built fierce fan loyalty.

Tomorrow night’s episode is only the fifth to be broadcast yet cult status is already secured. Bafta Cymru were taking calls about the screening from Sherlock devotees – an understated term if ever there was one – who were prepared to turn up at a Cardiff cinema on a wet Wednesday night from as far afield as Russia.

But then Sherlock exerts a mesmerising draw. In the eponymous role Cumberbatch radiates intellect, embodying Holmes’ mental powers physically.

How could someone with those cheekbones ever look a bit thick?

The actor revealed his reverence for Sherlock’s deduction riffs, in which the detective can extract an entire life story from a random ketchup stain. “It’s not like Superman where you wear underpants on the outside of your trousers, it’s something that’s sort of achievable,” he said.

“It’s an ability to visualise at will in absolute detail and construct logic and understanding from that. It would be a lovely superpower to have but it’s not a superpower, so it’s even more tantalising.”

These sequences, which celebrate the sheer joy of being incredibly brainy, also send out a powerful message to Sherlock’s youthful fan base – that it’s actually quite cool to be clever.

Young autograph-hunters waited all evening in the foyer of Cineworld for a glimpse of the cast members while a 17-year-old fan I spoke to analysed the narrative structure of the dramas in impressive depth.

Patronised by commissioning editors three times their age, teenagers aren’t supposed to respond to anything more challenging than nano-celebs in constructed reality shows.

Yet their appetite for Sherlock shows they might actually prefer a Scandal in Belgravia to Made In Chelsea.

Indeed Sherlock should restore all our faith in the small screen medium. It may share the schedules with a programme that considers Ryan Giggs’s sister-in-law to be a celebrity but watching these detectives allows viewers to deduce that television can still be an art form.