Benedict Cumberbatch as Stephen Strange in Doctor Strange. Credit:Disney/Marvel "They reorganised their schedule around mine, which shows a massive amount of faith. That was the most terrifying aspect. I thought, wow, these guys have really invested a lot in their belief that I'm the right person for the job so I'd better deliver and then some. It was good motivation for my part to try and get it right." In a movie that had yet to screen a week out from its worldwide release, Cumberbatch plays a world-famous neurosurgeon injured in a horrific car accident. Searching for a way to repair his damaged hands, he meets the mystical Ancient One (bald-headed Tilda Swinton) in an eastern enclave and discovers magical powers. The master magician who has mind-bending adventures was conjured up in the 1960s by artist Steve Ditko, who also created Spider-Man with Stan Lee. The character became popular with college students who were discovering psychedelic experiences and eastern mysticism. Cumberbatch knew nothing of that until he was promoting Star Trek into Darkness three years ago.

"It started with a conversation on a rooftop," he says. "A journalist when I was doing press for Star Trek said, 'you'd make a great Dr Strange.' I said 'Dr who?' "And he went, 'well, that too.' I went, 'no, no, no, I'm not going to play Dr Who. What do you mean Dr Strange?' And he went, 'have a look at the comics' so I did." It didn't strike Cumberbatch as an obvious role for him. "I thought 'I don't know ... well, I can ... oh, I see'," he says. "He's clever and arrogant, and there's a bit of flair and there's a Vincent Price tone to some of the characterisations of him in the drawings." Even so, Cumberbatch was not initially interested when he heard Dr Strange was following the likes of Iron Man, Thor, Spider-Man, Captain America, the Hulk and The Avengers into a new generation of Marvel movies.

"I could see the similarities to other characters I'd played and thought I'm not so keen on it," he says. "Then Marvel called and said, 'we'd love to meet you; we'd like you to play Dr Strange' and I was like, 'OK, now I'm listening'." Cumberbatch met director Scott Derrickson, best known for the Keanu Reeves version of The Day the Earth Stood Still and the Eric Bana horror pic Deliver Us from Evil, to discuss the movie. "I gave him my concerns," he says. "I wanted there to be more humour. I wanted it to be an evolution of a moment of occultism that the comics originally came out of. I wanted to know how it would be recontextualised now. I thought it was important to add a lot more hubris to this character and to take him on a really rich journey. "He went," Cumberbatch drops into an American accent, "'We're already on it.' He showed me the script and it was terrific. It answered a lot of my concerns. And every day we went to work, it was always about me having free range to add to that to improve it."

As a Buddhist, Cumberbatch was attracted by Dr Strange's evolution from a materialistic, egotistical, Lamborghini-driving doctor to discovering a spiritual realm. As he starts to talk about the subject, he spots something outside the window of the world's highest hotel. "My god," he says, voice rising in excitement. "A butterfly has just flown past us. Talk about spirituality. That was extraordinary. I'm in a steel and glass edifice of a building, 400 metres plus above sea level, and a butterfly – it looked like a cabbage white or a yellow butterfly, I couldn't quite tell – just flew past the window as calm as you like. Amazing. That was bang on cue." London-raised and educated at the upscale boy's boarding school Harrow, Cumberbatch's interest in eastern spirituality dates back decades. "I had a wonderful experience when I was a teenager," he says. "I went to Darjeeling to teach English in a Tibetan Buddhist monastery, a converted Nepali house surrounded by Indians, Chinese, Tibetans and Nepali. It was a cross-cultural blend unlike any other. "And for a white kid from a boarding school in England, the most mind-opening cultural exchange for me. I learnt a lot more than I taught. It was fundamental in my understanding of the broader scope of life and death and understanding mortality and something deeper within that's non-materialistic, not logic-based."

Around that time, the budding actor was also reading popular science books including Stephen Hawking's A Brief History of Time as well as such backpacker favourites as Fritjof Capra's The Tao of Physics, which deals with parallels between western science and eastern mysticism. "There are things that we can't witness that we have to sort of believe or have some kind of faith in that cross into certain realms of faith or understanding or spiritualism in the east," he says. "That was an appeal to this role for me in a way: this is a man of science and logic, a very materialistic man, who meets everything that's the opposite of that and discovers that there's a greater good to be had by concentrating his powers, and the powers of his hands, in that realm." It's a philosophy that feels timely for the movie's star. "The interconnectedness we all hoped that technology would give us through massive amounts of social media channels is definitely there to an extent but I think we all realise now we need something different, whether it's powering down devices and talking to one other or just being connected to nature as well as mindfulness and retreating into a place where you can hear the traffic and noise of your brain and try and still that ... "I think we all need that, whether it's doing it in an office block with loads of other Google employees or just doing it on a park bench in your lunch break or when you're swimming or when you're with your family watching your children."

Cumberbatch also likes being part of Marvel's march into a new era of comic book movies. "This is opening up the Marvel cinematic universe into the Multiverse, and these other dimensional elements of magic which are in the comics. The wonderful, left-turn storyboarding and art work by Steve Ditko was really revolutionary for its time and still stands the test of time – using what we're now capable of doing in cinema to honour that. "That's incredibly exciting. You've got the combination of a great character arc, a lot of action, a lot of humour and some hard-earned moments of heroism in this environment which is going to blow people's minds. That's a pretty alluring prospect for an actor." Cumberbatch's affection for superheroes came from movie adaptations rather than the original comic books as a child, starting with Tim Burton's Batman with Michael Keaton and Jack Nicholson as the Joker. "It really intrigued all our imaginations and enthusiasms as kids at school," he says. "We had the posters, we had the hats, we had the Prince soundtrack which we used to sing and dance to. That was my way in.

"It's very exciting as a 40-year-old adult to see yourself on billboards the size of buildings and realise that you're upfront and centre as one of the lead characters in that world now. Cumberbatch shows his sharp wit as he talks about Feige mapping out Dr Strange's appearances in other Marvel movies, including a reference in Thor: Ragnarok, which Kiwi director Taika Waititi has nearly finished filming in Queensland. "Kevin and the team introduced these characters with a great deal of forethought - no pun intended, that was an 'f', not a 'th' - that involves a much longer story arc," he says. "And it's now no secret to the world that I'm definitely going to be involved in a big way with the Avengers and we'll see where his character goes maybe in another individual standalone film as well. There's a great deal of excitement about the idea of what he can bring. "People often say that the frame is a little crowded with the amount of characters there are in Avengers films. Well, the frame is going to get a lot bigger with these characters so there'll be room for all of us. And I can't wait to interact with all these characters. I'm a huge fan."