During a Masterclass at the Media Guardian Edinburgh International Television Festival, featuring the show’s producer Sue Vertue, writers Steven Moffat and Mark Gatiss and actor Andrew Scott, the panel revealed that the inclusion of Moriarty came about after audience research.

Vertue stated, “There was certain things that came out of [the audience research] – one of which was they really wanted Moriarty.”

Originally, Sherlock’s nemesis Moriarty was not to feature in the initial three episodes. Moffat explains, “We didn’t know if he was one of the things everybody knew about. In a way you have to work out, because it’s kind of public property, what does everyone know and expect. To our surprise, when we got the research, they said, ‘Well, where’s Moriarty?’

Now Mark [Gatiss] and I, as tragic Sherlock Holmes geeks, will pipe up and say [adopting stereotypical nerd voice], ‘He was only in one story!’ Which is fascinating. [Laughs]”

Gatiss expanded, “If we’d done six sixties [minute episodes], we would have sort of eked it out. As soon as we did three nineties, he’s behind Phil Davis’s plot [from the first episode, A Study in Pink], he’s a shadow from the beginning.”

On the casting of Andrew Scott as the elusive villain, Moffat commented, “… originally in Mark’s The Great Game [Series 1’s finale] the big gag was we never saw Moriarty, we just saw Moriarty in the guise of ‘Gay Jim’, as we called him. And at the end of the script there’d just be a message and Sherlock would realise, ‘Dammit, that was Moriarty all along!’

But we had to audition someone to play Moriarty without ever having written a scene for him. So we rustled up a ridiculous scene, a really ridiculous scene to see if anyone could actually play this. And then we saw Andrew, who gave this blistering performance. And not only did we cast him, we thought, ‘We’ve got to put this nonsensical scene in!'”

Moving on to the Series 2 finale, broadcast earlier this year, Andrew Scott was asked by interviewer Boyd Hilton if he knew how the conundrum of Sherlock’s “death” was resolved, but before he could answer, Moffat interupted, “He’s dead by then!”

Continuing, Hilton queried if Scott was signed on for Series 3, to which the actor remained silent though he did reveal that he knows what happens.

Gatiss intervened, recalling a conversation with a fan who stated, “‘Obviously Andrew [Moriarty] can’t be dead because we don’t see the back of his head come off.’ Well, that’s because it was at half past nine on BBC One. It’s not going to happen.”

Moffat, after some more interrogation on the subject stated categorically, “he’s not going to be in [Series 3],” with Scott confirming, “Moriarty is dead.”

Were you hoping that Moriarty would return in Series 3? Let us know below…

> Buy the Series 1-2 boxset on Amazon.

> Order the BBC’s new official book, Sherlock: The Casebook, on Amazon.

Watch a clip from The Hounds of Baskerville…