“In the previous season, [ Billy ] was more of a bully, but now he’s really raw and evil,” Mr Montgomery says. “There’s the beginning of an exploration of a real antagonist.”

Obviously, Mr Montgomery is happy with his character’s development. “Oh, mate, I’m over the moon. This season is the pinnacle of my own creative process, of what I was allowed to do, what I was given the chance to do... I couldn’t have asked for more. It was an amazing time. Not just for me and my character, but for everyone – the stakes are so much higher, and I feel like the viewers, the people who’ve fallen in love with the show, are going to get everything they wanted out of it. They’re exploding the narrative, really picking apart every character, and that’s what I’m excited about.”

So, how did he go about creating a character so convincingly creepy that the Duffers couldn’t help turning him into a leading man (albeit one who’s a villain with a mullet)? I ask him why he’s so good at playing someone so bad, and he laughs. “I guess there’s a facet of that in all of us,” he says. “I’m just channelling it. I feel like it’s so far away from me as a person. What I’ve endeavoured to do is take a group of the maniacal incidents or characters in my life and combine them, and tried to make it as real as possible. And we improvise all day; we add lines. That’s the great thing about the Duffer brothers – it’s so collaborative. I always try to come to set with 10 things, and even if they use just one of my ridiculous ideas, I’m happy.”