Establishing one of the biggest cliffhangers in British TV history, season two of Sherlock climaxed with a shocking thud. A nation gasped as the titular 'tec (Benedict Cumberbatch) apparently plunged to his death while his faithful sidekick and sounding board Dr John Watson (Martin Freeman) looked on. We all kinda know old clever clogs did survive (that season three even exists is a pretty big clue, as is the title of the opening episode, 'The Empty Hearse') but how on earth did he do it?

'It's been a long time since Sherlock Holmes jumped off that roof,' adds executive producer, writer and co-creator Steven Moffat. 'It's time to reveal the truth about what happened between him and the pavement.'

Given how big the show is, it's unsurprising that no one involved is willing to reveal how Sherlock managed to get out of this seemingly inescapable conundrum. So, we'll all just have to wait a little longer for series three to screen at the New Year to see how Sherlock’s formidable intellect saved him from the jaws of certain death.

Sherlock Holmes is one of the most enduring characters in all of fiction. Countless films, TV programmes and plays have been adapted from the source material. This modern retelling was perhaps one of the most radical, taking Sir Arthur Conan Doyle’s classic tales of mystery and reinterpreting them for a contemporary audience. 'Sherlock's a mass of contradictions and that makes him fascinating,' explains Mark Gatiss, who not only plays Sherlock's brother Mycroft but also co-created this new vision of Holmes. 'He's cold, aloof, arrogant and dangerous, so therefore, absolutely magnetically attractive. It works in real life as well, but ultimately people would not remember Sherlock Holmes and Dr Watson if Conan Doyle had not been a genius writer; what he created was pure gold.'

Unlike Guy Ritchie's recent movies which recast Robert Downey Jr's Holmes as an action hero, Cumberbatch's Sherlock relies on superior intelligence and reasoning rather than quick fists to best any criminal. Moffat and Gatiss have thrown Sherlock against some fiendish villains and dastardly dilemmas while their wonderfully visual approach revealed just how Sherlock's mind works.

The show also works due to perfect casting with Cumberbatch as the detached driven genius while Freeman adds the everyman charm. Their rapport and verbal sparring forms the drama's core. 'What John brings to "the game" isn't the same as Sherlock, but it's kind of useful, as Mycroft says with disdain, "the legwork,"' says Freeman. 'There's only so much you can develop John's role in the deduction because then it's not Sherlock anymore. It has to be primarily about him, and that's the only way to do it, with John as back-up.'

The public's love of a mystery coupled with two great leads meant the detective series was an instant success. 'We hoped it would be well-received and as popular with viewers as it was with us,' said Freeman. 'We loved making it and are very proud of it, but beyond that it's out of your control as to how people will view it, so the response was great.'

Despite his own input, Gatiss is ever modest and happy to share the credit with the show's source material. 'The entire canon of Sherlock Holmes is fantastic and sales of the old stories have gone up. I couldn't think of anything more brilliant than for people to be pointed back towards Doyle, who is the wellspring of all of this. And still a criminally under-rated genius writer.'

Sherlock starts on BBC One, Wed Jan 1.

Sherlock: Series 3 Launch Trailer - BBC One