Whether embodying an endless string of oddballs in The League of Gentlemen, tangling with Shakespearean speech on stage, or directing his annual Christmas ghost story for the BBC, Mark Gatiss has never done things by the book. Even his award-winning adaptations — most notably the Cumberbatch-catapulting Sherlock — adhere to neither custom nor convention.

So it’s no surprise that the 58-year-old’s next move maintains this unpredictability: two roles in this summer’s biggest blockbusters. In July, Gatiss will leap aboard the Marvel machine with The Fantastic Four: First Steps, and this week he returns to the Mission: Impossible franchise in The Final Reckoning, which saw him step back into the strait-laced, sombre shoes of the previously unnamed NSA director.

“But I have news!” claps Gatiss when we meet on a sunny Soho afternoon, the day before the action film’s premiere. “In the last one, we all just went by our titles. But while filming, the director, Chris McQuarrie, said: ‘What do you want to be called?’ In my bones, I’ve always had a fascination with the strange baroqueness of American names. Nowhere else on earth is anyone called something like Walton Goggins… a writer called Booth Tarkington wrote The Magnificent Ambersons. I love those things.”

Gatiss, then, came up with a list of potential, all-American names — including the evocative ‘Bellman Sides’ — and the character was eventually christened ‘Cotton Angstrom’. “It’s vaguely Scandinavian,” says the actor. “So it could be an American settler’s name. Cotton I got from the film Scream.”

And so Angstrom lives — one of many government officials attempting to cajole or control Tom Cruise’s super-spy into saving the world. The film, allegedly, is a franchise-finisher; a mission finally accomplished; a book firmly closed. But another chapter opens for Gatiss this summer: Bookish, a new post-war detective drama he created and stars in as the studious Gabriel Book (another cracking name, one fit for a case-cracker). Gatiss has history with the genre: before Sherlock, he adapted three of Agatha Christie’s Poirot murder mysteries for ITV, and appeared in an adaptation of the first ever Miss Marple novel, The Murder at the Vicarage.

“Agatha Christie remains paramount to this day because she had about 35 of the best ideas anyone has ever had,” says Gatiss of the author. “She was a machine! But [Arthur Conan] Doyle is just unsurpassable. He wrote the book on so many aspects of deduction.

“To quote Sherlock Holmes, ‘there is nothing new under the sun’,” the razor-sharp Gatiss says of whether his new detective is derivative. “Everything is a variation on a theme, but its roots are very much in that golden age of detective fiction. I wanted to do my own detective, give him his thing. Because they all have a thing.”

And Book’s is books. Gatiss’ amateur sleuth owns a bookshop which the actor describes as “sort of an analogue computer”. The filing system is as eccentric as the proprietor, with Cataracts of the Nile placed next to books about eye disease, and so on. “It doesn’t make any sense, of course!” says Gatiss. “But it does in his head. He quotes things, makes strange parallels and allusions and then, somewhere in that matrix of paper, he finds a solution.”

Rather aptly, I’m meeting Gatiss in the grandiose library of the Soho Hotel, where the walls are lined with storied volumes. His current literary obsession, however — a collection of Japanese murder mysteries — are unlikely to be found even on these well-stacked shelves. “I find them intriguing,” he says of the stories. “Often, translated things have a sort of stiffness to them, but these are very formal, so it suits them.”

Whodunnits have long been Gatiss’ vice. At age 13, he read one of Christie’s early Poirot novels, The Murder of Roger Ackroyd. When the final reveal came, he dropped the book in shock. Bookish, he hopes, will have a similarly twisty, Christie flavour.

“It’s pitched somewhere between Ustinov’s Evil Under the Sun and A Matter of Life and Death,” says Gatiss of the show’s tone. “Lots of melancholy, but also fun. The period, 1946, is also unusual — as it’s rarely covered. Crime was through the roof at that time, because there were so many guns around from the war. For a while, London was like Chicago in the ‘20s.”

Gatiss researched the era comprehensively (he’s also currently reading about the de-Nazification of Germany, which he describes as equal parts “intriguing” and “upsetting”) but Bookish isn’t his only period piece of the year. In The Fantastic Four: First Steps, Gatiss plays a talk show host called Ted Gilbert (a thinly veiled Ed Sullivan) in a pseudo-retro, alternate-universe 1960s — or, as the actor puts it, “the future we were promised in The Jetsons.”

“I haven’t read the full script,” he reveals. “So I only really know as much as you do. But Rory Kinnear once said to me about his role in the James Bond films: ‘I’m going to get an award for services to exposition’. It’s the same with this. I’m not in Fantastic Four much at all, but I do explain what’s going on.”

This brief foray into superhero-dom was filmed in Britain, as were Gatiss’ scenes for Mission: Impossible. Did this dash any boyhood dreams that Gatiss — who grew up in a small town in north-east England — might have had about jetting off to Hollywood?

“No! I never had any Hollywood ambitions or fantasies in that way. I’ve always loved American films and TV, but I’ve never thought about it. The idea of being whisked off for six months? Friends have done it, but they end up sitting by a pool and coming home with a slightly damp anecdote about the loneliness of Los Angeles — as opposed to some amazing story.”

The current cultural landscape is rocky, says Gatiss — especially when it comes to television. “We’re still slightly caught between worlds,” he says of streaming versus traditional TV. The multi-disciplinarian that Gatiss is, however, means his schedule remains full. The day after we speak, and weeks before it hits screens, Bookish is renewed for a second series. The actor is still hoping The Motive and the Cue (the play, directed by Sam Mendes, for which Gatiss scooped his second Olivier Award last year) will transfer to Broadway. “But Sam is busy with his Beatles films until the end of time,” laughs Gatiss. “That’s a big story. Sam told me that the most interesting film, of course, will be Ringo.”

Before Broadway, Bookish and Fantastic Four, however, Mission: Impossible sees Cruise, Gatiss and co pit their wits against a rogue AI. Machine learning is a topic widely and variously discussed in the real-world entertainment industry, so what does Gatiss — a man across more creative pursuits than most — think of the would-be tech threat?

“Well, we mustn’t be Luddites about it,” he reasons. “But, like all stuff, it has its traps and hazards. Equally, though, it’s doing something clever. If you’re re-voicing something and it doesn’t quite fit, then fine. But that’s not the same as the film itself being generated by a machine, which is what everyone’s afraid of.

“I came out of the gym the other day,” he adds, “and there was one of those four-legged robot things on the street. Everyone was staring at it slightly afraid. Then someone went and patted it like a dog, to which I say: ‘Kill it with f**king fire’. We know how this ends! We do! It’s all very Minority Report."

Trust Gatiss: he knows his sci-fi stuff. He wrote on (and occasionally appeared in) Doctor Who for over a decade, and the futuristic genre appears almost as often as horror or detective fiction in his big book of references. Gatiss has a vast reserve of titbits and trivia in general — much like the Bookish bookshop, or the famous ‘Mind Palace’ he and Moffat used to explain Holmes’ brilliance in Sherlock. The culprit in this case? Endless internet rabbit holes, says Gatiss, which he often gets lost down.

“They often suggest a story but it can be terrible because then the algorithm gets you,” he says, before tentatively adding: “The one thing I am genuinely interested in and do believe in — I don’t believe in God, or ghosts, although I’m obsessed with them — is unidentified flying objects, of a sort. There’s something definitely going on there.”

This comes as a surprise, but Gatiss is clever, charismatic and erudite enough to put up a good defence — even if most people consider such conspiracies hokum out of hand. In fact, the final book currently crowding Gatiss’ nightstand is also a left turn: The First Psychic by Peter Lamont. It’s an investigation into a Victorian medium who allegedly read minds and levitated, but died before revealing the secrets behind his ‘skills’. “It’s never quite been explained,” says Gatiss with a smile. A glimmer of belief, perhaps? Or just further appreciation for a good mystery?

Whatever his convictions, it’s the depth and diversity of knowledge that make Gatiss such engaging company. It’s also why he continues to brim with such fascinating facts, why he continues to take on such disparate, metamorphic roles, and why — like his latest creation’s sprawling bookshop — he continues to defy classification.

Mission: Impossible The Final Reckoning is in cinemas now; Bookish premieres on U&Alibi in July 2025.

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