Since he last graced these pages in the suspenseful aftermath of Sherlock’s second series, the snowballing success of the BBC drama has seen Mark Gatiss become one of the most coveted minds in television.

Having co-created the series alongside fellow Doctor Who writer Steven Moffat, the former League of Gentlemen star has had so many hits that he’s regularly approached by people who assume he can just walk into the BBC with a green card and take any pet project to prime time.

The reality, he insists, is quite different, but you can see the logic. Quite why Gatiss has so consistently hit a nerve is beyond even the man’s own comprehension, and besides attributing it to the childhood passions that drive his shows, he’s in no hurry to overthink matters.

“Ronnie Corbett once said to me, ‘If you analyse things, they disappear’ and I think that’s very true,” the 48-year-old explains.

“Conan Doyle spent his entire life baffled as to why Sherlock Holmes was the thing that people loved when he wanted to be remembered for his big historic novel. You have to think, ‘Don’t argue with the facts, it just works and that’s wonderful’.”

As his talk this week at the Phoenix Cinema will show, Gatiss is more happy to pinpoint the strengths behind works that aren’t his own. Tomorrow night (Friday), he is paying tribute to Federico Fellini’s 1957 classic, Nights of Cabiria, before a screening of the Oscar-winning foreign drama.

Lasting impression

The story follows Cabiria, an Italian prostitute, who wanders the post-war streets of Rome as she searches for true love in vain. Gatiss first saw it 15 years ago upon its reissue; it is among his favourite films and one that left a lasting impression.

“A friend of mine, Terry Bowler, had said to go see this film because it would change my life and it did. Up until that point, if you’d stood me outside a multiplex and it was the most important foreign film ever made versus Godzilla, I’d have probably gone and seen Godzilla and then, as you always do, regretted spending my money on a piece of rubbish.

“But this film, it’s so beautiful and absolutely heartbreaking; it’s fantastically shot and amazingly acted. Ever since then it’s been a real touchstone for me in terms of opening my eyes to world cinema.

“It’s a realist film with Rome still bomb-shattered, but it’s got this amazing vibe to it. You can see why people wanted to go there: it’s just very sexy and sort of bursting with new energy.”

A long-time devotee of the small screen, Gatiss says his own aversion to making movies stems from seeing “very good friends who’ve given years of their life to a project only to see it not happen”.

Comparatively, pitching a TV show such as Sherlock – in which he also plays Mycroft, the on-screen brother of Benedict Cumberbatch’s detective – was a more straightforward affair.

“It was a very simple commission because Sherlock Holmes is the most popular character in the world – that’s a simple fact. He’s the most filmed character there’s ever been and a modern-day version also meant it wasn’t as expensive as a period production.”

The similarities between Doctor Who and Sherlock are noticeable: both feature an offbeat but brilliant problem solver; complementing companions; inspired, imaginative villains and fantastic, modern production.

More noticeably though, what seems to have captured the attention of viewers across the globe is their quirky faithfulness to British culture – a fact not lost on Gatiss.

“Every time I have a meeting with someone who’s trying to water down a British element, I just think, ‘look at the facts’. If you tried to make James Bond a mid-American man he wouldn’t have any of his charm, so it seems silly to me to try and bland things out to make them more palatable when in fact it’s the most distinctive flavours that people respond to. It’s like an Indian meal!”

While Sherlock takes up most of his time, Gatiss has also penned stories for the upcoming series of Doctor Who. His script for the third episode was one of five that were regrettably leaked in early July, to much outrage from fans.

“It’s annoying,” he says, “but not the end of the world because the only people who will read those are people who will spoil it for themselves.” Regardless, the writer is incredibly excited about the new series, which features a new doctor in Crouch End’s Peter Capaldi.

“I’ve seen quite a bit of him and he’s absolutely fantastic. Peter’s just got this amazing, fierce, funny, slightly alarming quality to him – he reminds me a lot of Alastair Sim, actually. You’re not quite sure where you stand with him; he’s very funny, but he’s got this glint in his eye and I think it’s a terrific run of episodes.”

Will it be the new dark doctor many are expecting? “The brilliant thing about Doctor Who is that it’s always changing like the central character – not just the face of the actor, but the direction of the show.

“David and Matt were both wonderful, but both were very human Doctors and I think it’s time to remind people that the Doctor isn’t always like that. He’s that sort of Tom Baker, John Pertwee and even Christopher Eccleston style actually: it’s someone who’s not immediately going to be your best friend and can be quite abrupt and rude.”

Away from television, Gatiss lives in Islington with his boyfriend, actor Ian Hallard. He phones the day after attending the final show of Monty Python and admits to finding the night “terrible moving”, having grown up on the comedy troupe as a child.

Famous creation

With The League of Gentlemen gang still on close terms, did the show not send him craving for a reunion of their own? While he’s open to the idea, Gatiss says he enjoys working with the group outside their most famous creation.

“Not to strain the Monty Python analogy too much, but when I was a kid I loved the fact that Michael Palin and Terry Jones did Ripping Yarns and John Cleese turned up briefly in one episode, or that Michael Palin and Terry Gilliam wrote Time Bandits together. They pop up in each other’s things and I think that’s lovely.

“I did an episode of Psychoville with Reese [Shearsmith] and Steve [Pemberton] and they’ve been in a couple of my things like that. It’s nice; it feels like you’re continuing the lineage without doing exactly the same thing, but we would love to do something again one day.”

The time will come, but it’ll probably have to wait. After recent appearances on further powerhouses such as Game of Thrones, Gatiss is an actor as well as a writer in demand. He is due to appear in a television adaptation of Hilary Mantel’s much-celebrated novel Wolf Hall next year and should it succeed, it will be just another string to his formidable bow.

With an impressive following online (his Twitter audience weighs in at more than half a million), he is aware that he’s fast developing a huge fan base, but only feels obliged to speak out on a few heartfelt issues.

“You’ve got to be very responsible about it, but sharing something like how to get young people to vote, well that’s just a good idea, isn’t it?

“My big fear at the moment is that fascism is on the rise everywhere across the world. The world is always in a state, but it’s quite alarming at the moment the way that European wars are brewing; stuff that we thought wouldn’t happen again is edging closer. Anything we can do to stop people becoming totally disillusioned with politics, we should do. It’s very, very important.”

The fact that he is now in a position to inform such issues, however, is a triumph in itself. If his influence can also attract a few fans to the Phoenix Cinema to hear him wax lyrical about his favourite film, it’s a victory for self-proclaimed “geeks” everywhere.

“I always find it weird to hear people talk about Sherlock or Doctor Who as a cult TV show – I don’t know how much more mainstream you can get. It’s been said before that the geeks shall inherit the earth and it’s amazing how all the big American films – the genre films, superhero films – they’ve gone completely mainstream.

“Now you’re almost in a cult if you don’t like them.”

Mark Gatiss presents Nights of Cabiria as part of the Phoenix Nights series tomorrow. Visit phoenixcinema.co.uk for details.