"I liked how difficult it was, how much focus I had to have. It's a good feeling to come away from a day's work feeling like you've achieved something. Tired brain is good."
This isn't Christian Bale, Gary Oldman or the preternaturally focused Daniel Day-Lewis talking. It's actually Dominic Cooper describing the challenge of his dual role in the forthcoming The Devil's Double.
The chilling thriller telling the tale of Saddam Hussain's psychotic son Uday and his schoolmate Latif, who was unwillingly forced to take the job of Uday's body-double, by sheer chance of his physical similarity.
Cooper's performance is highly charged, carrying both roles with an assuredness and subtlety that caused one critic to consult his notes before realising both parts were being played by the same actor.
Bizarrely, this is the same Dominic Cooper we've previously seen as a sun-kissed crooning groom (Mamma Mia), lovelorn for Keira Knightley (The Duchess), helping lead Carey Mulligan astray into swinging sixties London (An Education) or, further back, using his Mediterranean good looks to seduce and manipulate his teacher (The History Boys).
Whether in a pair of beach-shorts, a periwig or a school uniform, his career up to now appears to have been unavoidably aided but dictated by his allure to all types - would he agree that there has been a theme?
"A posturing boulevardier? Wow, I'm going to use that," he laughs (I couldn't think of another description, but we both knew what I meant - it basically refers to the inescapable sexual promise and threat inherent in his roles so far.
"A greasy quality somewhat?" (This was my other suggestion, leaving him equally unfazed) "I don't mind that. I don't find them that similar. There's an untrustworthy quality about all of them - I find them slightly more interesting or more dynamic with certain layers, rather than just playing the love interest.
"I suppose it begs the question as to what people's opinions are of you or what you can do (he makes a good point, it's not his fault he's good-looking after all) - the challenge is to get out of that mindset. We all want to put people, things in boxes, it makes it easier to sort out in our heads, and I really hope that this role is a step away from that, so people can see that I'm up for trying for other things and challenges."
"Certainly, Devil's Double felt like an incredible opportunity which is why I was so proactive in comparison with my normal everyday life. I was hounding people as to where it was going, asking for an audition, doing all stuff I wouldn't normally do."
If The Devil's Double is Cooper's big chance to flex his acting muscles and show people what he's capable of, he's grabbed his moment with knobs on. Particularly when playing Uday, he disappears into the role so completely you start viewing him through the eyes of Latif, as is intended. (During our interview a day after my screening of the film, he offers me a cup of tea in Uday's high-pitched tones - an experience surreal and quite chilling, frankly.)
Until he was killed by US forces in 2003, Uday was a man known for grabbing schoolgirls from the street to satisfy his lusts, a neurotic unstable playboy distracted from a wealth of orgy-revelling only by slitting open his father's aides after a perceived slight - so how was Cooper able to tap into such psychosis?
"It was actually quite easy to access that level of evil, which is a bit worrying," he smirks.
"What was hard was the fact I found him so unpleasant and disgusting, with no redeeming qualities whatsoever. The more I unearthed about him, the more I was repulsed by every single aspect.
"One of my fears was that Uday was becoming watchable than our hero in the film, he was so obscure and revolting.
Despite his grasp of both parts, Cooper's sympathy remains firmly with the decoy, particularly after spending time with the real-life Latif, who was smuggled out of Iraq before Uday's death, and now spends his time roaming between different countries in Europe.
"I didn't want to pry too much into his life. There are a lot of murky, horrific images that would be best not presented. We've got enough there, I think.
"I was amazed that anyone could find themselves in that terrible position. I can't identify with that - to have your face manipulated and changed into someone whom you despise, and to be thrown into this world of opulence and riches, and have the horrible feeling of temptation and desire when you shouldn't, and then having to perform when you're not a performer, as someone you hate and you know everyone else hates. It's all very odd."
Cooper was also fascinated by the technical challenges of filming both parts at the same time...
"I was intrigued by the story, and the technicalities of how it was ever going to work.
"We would only have a room for one day, so Uday's teeth were on standby all the time. I would ask to do Uday first, because he was the driving force and the architecture of the scene, in a world of his own, so would dictate everything else.
"I'd then immediately have to go and get changed into Latif, and repeat the exact camera action.
"Backwards and forwards, to and fro... the problems were second-guessing the performance I would give as Latif when I was playing Uday, not knowing how that performance would play out, and then trying to remember it when I went back to the other one. It was exhausting, but exhilarating. It was a strange way to work, but I found it very compelling.
Cooper has the excellent manners of a well-raised British schoolboy, but has fame changed him or the way he goes about his life? Despite his rising star and a previous high-profile romance with his Mamma Mia co-star Amanda Seyfried, he says not.
"I have a very easy life, I can wander around. Occasionally, if you go somewhere 'pappable', but otherwise I'm very independent, I love wandering around in my own space - it's not ever been a problem in my life.
"Still based in North London - I'm really happy, I don't get to spend much time here, so it's great to see old friends." These include bosom buddy and co-alumnus of The History Boys James Corden, with whom Cooper used to share a flat and still sees whenever he is in town.
And what's next?
"There's no plan. I really don't know, go off somewhere, have a rest - why not?" Rumours of his forthcoming role as gangster John Gotti are dismissed with a wave of the hand, (which refutes all other press reports, so watch this space).
I get the feeling that, for the time being, he is replete and satisfied with his efforts on The Devil's Double.
"I don't feel any worry, because it's completely out of my hands. What does it prove if people don't or do go and see it? Personally, I can't affect people's taste and if it's something they want to see.
"There's nothing worse than feeling like you haven't done something to the best of your ability, and with this particular project, I worked hard and I'm happy."
And, with that, Dominic Cooper pours himself another big pot of tea. He has the air of a man at ease with a job well done.
The Devil's Double is on nationwide release from next Wednesday 10th August.