“So they had to dress thousands of blossoms into the trees and then blow this kind of ash to fake the blossoms falling in the sky. We were a little bit tickly in the back of the throat after the first day, but then the second, I was like, ‘Wow, I’m feeling pretty worn out and weird.’ Not Covid! Six weeks later, though, I was still kind of hacking up a good lung full of whatever.”

The rest of director Sam Raimi’s sequel is a wild combo of crazy creatures, dark fantasy, trippy alternate dimensions and multiple character variations, including different Stranges for Cumberbatch.

Madness, along with an integral appearance in last year’s hit Spider-Man: No Way Home, offered Cumberbatch a return to the Marvel universe after his Oscar-nominated performance as a cruel cowboy in Jane Campion’s Netflix Western The Power of the Dog.

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He enjoyed everything about his awards season run, “from the first moment we had in Venice [at the film festival] to the very last moment of dancing our socks off around Jane’s Oscar”.

But he appreciated being back in the Marvel Cinematic Universe, for his seventh turn as the pernickety magic man.

“You just have to make that moment believable in that fantastical realm of sorcerers and monsters. I like being able to bring the world fun as well as more serious fare.”

“He’s a human being and is frail and breakable, but he’s also adaptable and a maverick [who] does act outside the rules. That sometimes has consequences,” Cumberbatch says. “What makes him an interesting character is the fact that he is imperfect, that he can learn from his mistakes and he’s not afraid to make them or embrace throwing the dice and taking a chance.

“Reckless? Yes. Wrong? Sometimes. Useless? Absolutely not. He’s pretty damn brilliant at his job.”

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Raimi says Cumberbatch’s “firm grasp and knowledge of who he was as Doctor Strange” was essential to play the character’s multiverse variations.

“He knew to tweak one little aspect of it, and understood what those changes would be,” says the director.

Re-imagining Strange in different ways was “joyous”, Cumberbatch says. “It’s a very crowded film, let’s put it like that, and I’d love to have done more of those characters.

“There’s one moment where I had to switch between two of them, and that was pretty hell for leather. It was very concentrated work, some more subtle than others in their shifts. But they’re all visually different. It wasn’t like a complete horrible schizophrenic mirror jam of not knowing where I was or who I was, but some moments were more challenging than others, for sure.”

Cumberbatch is less confident when you ask him to imagine what traits he’d find in every version of himself in a multiverse.

“I can talk about my characters as if I’m some kind of closet armchair psychologist but I’m really c*** at doing self-analysis,” he says with a laugh.

“I talk too much, so I’m pretty sure most of them would be too loquacious. Maybe some would just be a lot more pithy and not worry so much about what they’re saying and just get on with the job. I could learn from that.”

But he offers “a sappy answer” that’s “probably the truth”: “The priorities would be the same, that family comes first [and] would make that the foremost aim of their lives to be a good partner and father,” says Cumberbatch, who has three sons (Kit, six, Hal, five, and Finn, three) with wife Sophie Hunter.

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He has just finished filming Wes Anderson’s Netflix comedy adventure The Wonderful Story of Henry Sugar, playing the title character in the Roald Dahl adaptation. And next up is a return to New York to host Saturday Night Live on Saturday, his second stint following a 2017 appearance that featured the game-show sketch “Why Is Benedict Cumberbatch Hot?”.

“It’s so odd because it’s live and there’s cortisol and adrenaline in play, but also it’s very late in the day,” Cumberbatch says.

“I really underestimated quite how tired I would be before stepping on to do the opening monologue. I was sort of yawning backstage with nerves and exhaustion. So this time around, it’s just a bit more of the marathon strategy and also being present enough to take it in and enjoy it.

“I’m not going to try and overthink anything else too much about it because the experience needs to be fresh. That’s when the magic happens.”