Henry Cavill would rather be at home right now, without the fame, without the attention, sitting at his gaming PC in shorts and a T-shirt, playing Total War: Warhammer II.

Yes, Henry Cavill. Superman.

And yes, Warhammer. The game with little plastic goblins.

And he’s played it through six times already, accounting for hundreds of hours of gameplay (“With six different races! And I love it each time!”).

Cavill is talking to me a few hours ahead of the premiere of Netflix’s adaptation of Andrzej Sapkowski’s The Witcher. He’s elaborating on how his love of escapist gaming – something he’s possessed almost since he was old enough to sit at a computer – has only become more and more enhanced as his anonymity has disappeared.

“Every time I step out my front door, I’m hyper aware,” he says. “Even if I’m not looking terrible, you still realise there are people taking sneaky photos of you, because that’s what people like to do. And then they put them on the internet and you see them on Instagram and you’re like, ‘Oh, my god.’”

He groans.

“At home, I get to sit playing games for ridiculous amounts of hours and escape there, because going outside has the opposite effect.”

The Hollywood star is the perfect get for Netflix’s latest original show. A biologically flawless, world-famous presence, he’s the kind you wouldn’t necessarily expect to be headlining an adaptation of niche, Polish high-fantasy literature that spawned a hugely successful video game franchise. But he's who Netflix needed to join a less recognisable supporting cast. In fact, it was a role the actor chased the moment he found out about it.

“My first involved experience [with the franchise] was The Witcher 3,” he tells me, explaining how he’s now played developer CD Projekt Red’s 100-hour role-playing epic two-and-a-half times to completion, experimenting with different difficulty settings, first on regular difficulty and then on the game’s toughest setting, in order to find the perfect balance of fun and challenge.

© Katalin Vermes

“It’s all well and good when you’re trying not to stress out,” he says, “but then I realised I wasn’t chilling out. I just ended up dying at the wrong points and thinking, ‘I should not have left the roads. I don’t know why I left the roads.’ I couldn’t run away fast enough or my attention span dropped for a second or I answered a text and now I’m dead and that’s six or seven hours of gameplay that I’ve just messed up.”

Netflix’s adaptation is based primarily on the books, but the universe’s DNA is distinct enough in book and game form that both are sort of interchangeable in terms of tone, lore and plot. Cavill plays the titular role, Geralt Of Rivia, a famed monster hunter with mutant abilities, pristine white hair and cat-like eyes. The actor had, understandably, always assumed the books were spin-off stories from the games – the latter have been much more successful – but after quickly setting up a meeting with show creator Lauren Schmidt Hissrich to express an interest in being involved, he read all of the books and “absolutely loved them”.

Video game adaptations are rarely good. Cavill stops short of saying which he thinks are bad, but he says The Witcher is different because of the source material. “It’s based on a fleshed-out character,” he says. “Yes, you make decisions in the game, but it’s fairly unique within the gaming world. There’s a bit more of a character here.”

For Cavill, coming to something this close to his fanboy heart, staying true to the “lore” was important.

“I want to do it as true to the lore as possible. For me it was about bringing my love for the character to the show, as a fan – I want to protect it. It would’ve hurt my heart to hear there was a show that I didn’t jump on, [especially] if someone else had a unique and perhaps even brilliant interpretation of Geralt, but one not who I, as a fan, sees.”

Cavill also pushed more and more for Geralt’s signs – magical spells – to be used as much as possible in the show, despite the expense attributed to the CGI. “I really wanted to push that in there, because for me the audience must know he can do these things. It mattered to me, because it’s all part of being a Witcher.”

Warhammer and The Witcher aren’t his only big gaming passions. He reminisces fondly about playing games with his brothers, cramped around his mother's dining room table in makeshift LAN parties. He grew up on games such as Delta Force and Half Life. In the former, his brothers toyed with one another endlessly. Especially, he says, when his younger brother was repeatedly killing his elder – a serving member of the armed forces – to great personal frustration. Eventually, though, the tables turned. “He actually started using military tactics, so my youngest brother was getting slayed at every corner,” Cavill says, laughing.

Now, though, it’s time for him to head to the premiere, another global appearance as one of entertainment's most bankable stars. Until later, of course: when it's back to his Kensington home, back into shorts and T-shirt and back into Warhammer.

“There’s just something about those games that I find so satisfying,” he says. “There’s new DLCs coming out all the time and I’m looking forward to whatever the next one is.”

The Witcher is on Netflix from 20 December.

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