Having embodied an indomitable Spartan warrior, a plucky undercover nazi-hunter, a valiant us marine battling his way across war-torn Europe and, now, a heroic roman soldier taking on marauding Picts in ancient Scotland, you'd expect Michael Fassbender, star of Centurion, to be a man of not easily rattled. Which may well be the case. Still, if you want to put the willies up the actor, just bring up the prospect of impending stardom – a very real prospect given eye-catching roles in, among others, 300, Inglourious Basterds and Band of Brothers, plus the lead role of centurion Quintus Dias – and watch the colour drain from his face.

"That sort of talk makes me nervous," he says, taking a swig of lemonade at the bar, joint not unaccustomed to the odd celeb. "I try not to think about those things, because I know the bottom can fall out at any moment. My aim is to concentrate on the work and let everything else take care of itself."

Right now he is content to enjoy his relative anonymity while filling Empire in on Centurion and its harsh location shoot. "I thought it was great!" he grins. "We shot most of it up in the mountains near Aviemore, which was freezing but beautiful. We'd get into these half-tracks, minimal crew and just the actors who were needed, drive into the mountains and shoot the scenes in the snow." Which sounds great, albeit a little nippy when you're wearing a skirt. "We weren't actually wearing skirts," he insists. "We figured the Romans would've adapted their gear to their environment, so we had tunics and long pants. It was authentic, we weren't just wimping out. And I did one scene where I'm running through the snow, half naked – from the waist up, not the waist down, thank God. That was tough. But, you know, we got back to the hotel at the end of the day, so it wasn't so bad."

Centurion tells the story of the Ninth legion, the Roman army's elite shock troops, and their ill-fated mission to quell a Pict uprising in the wilds of the Scottish Highlands. "The legend is that 15,000 legionnaires went in there, and not one of them came back. That's when the Romans, so the story goes, built Hadrian's Wall and said, 'This is where civilization ends. We're not messing with those bastards again.'"

Given Marshall's track record (Dog Soldiers, The Descent), Centurion follows in the tradition – dark in tone and lavishly violent. "I'm not sure how dark, though. The Ninth get ambushed over the border and there's only handful of soldiers left, fighting for survival. It's basically a thriller, a chase movie. It's Deliverance meets Apocalypto – which is my favourite chase movie of all time. And Centurion does have that kind of Deliverance thing: being out of your depth in an alien land and not respecting the locals. Minus the anal rape scene, of course." Of course. What it does have is some spectacular dust-ups between the Ninth and the Picts, and, as you might expect, lashings of Marshall's trademark blood-letting. "Well," he says, "you know Neil's not gonna make a movie without a few heads getting lopped off."

Like 300, Centurion involved intense physical training for Fassbender, not least in the head-lopping department. "You have to look like you know what you're doing with a sword," he says, "because these guys were taught to fight from the age of six. You have to sell that illusion to the audience. It doesn't come easily to me, but once I get t, it stays with me. I wouldn't fancy getting into a real swordfight, but I'm great with a broom and a dustbin lid."