Cillian Murphy is one of those unique beasts; an attractive actor who has been in both critically acclaimed indie films and huge box-office successes – but is still definitely an actor, not a movie star. Some of this distinction comes from his commitment to maintaining a career in theatre, but much of it arises from his publicity-shy personality.

Murphy, now 40, is rarely seen at awards shows and does a minimal amount of interviews, never appearing truly comfortable with the camera being on him unless he’s in character.

He has previously commented on how much he dislikes the increasingly “dumbed-down” nature of press interviews, saying that “the reductive nature nowadays of most journalism is very frustrating.” It’s an understandable complaint – in an era where most interviews are between four and 15 minutes, it’s difficult to explore any issue in-depth. But it also seems that Murphy appreciates the brevity, as it allows him to maintain his privacy. When asked about his views on politics, fatherhood or even just his current passions, he can neatly avoid giving too much away by claiming “oh, there’s too much to say in such a short time.”

Thankfully, though, he is more than happy to chat about his role in Sally Potter’s satirical drawing-room comedy, The Party, which sees a dinner party of British elites get out of hand. The characters’ chronic insincerity may be read as an allegory for British politics, as everyone expresses lofty ideals – but acts with self-serving cynicism.

Murphy plays a coked-up banker, and explains he was excited both by the opportunity to act with long-time heroes Timothy Spall and Kristen Scott Thomas, and the wickedly funny script.

“I’m very interested in films that are entertaining and funny,” he says, “but which also have intelligent ideas and ask questions. Sally smuggled those questions in really brilliantly; questions about society, about the gap between what people may want intellectually and what they want instinctively. My character represents crumbling financial institutions, and Kristen represents the Labour party and what state that’s in. It’s not polemical or didactic – it’s more that if you find it entertaining, it may also spark a conversation with your friends after.”

Though Murphy is known among mainstream audiences for playing villainous characters in Inception, The Dark Knight trilogy and Red Eye, he has always loved comedy, bringing out his playful side in films like Intermission and Breakfast On Pluto. He reveals he loved the absurdity of his character, who’s a high and sweaty mess for the entire film – though denies trying any chemically-enhanced method acting.

“The state that he’s in emotionally and chemically means he’s in a heightened state both physically and mentally, which is great fun,” he smiles. “It gives you licence to take him to a slightly different level. For me to act in a physical comedy was great fun. So much of the work you do onscreen is about stillness and subtlety and the close-up – it’s very worthwhile and some of my favourite actors do that beautifully. But it’s also great fun to just let loose physically. Still, you can’t walk around in character like that all the time – you’d collapse!”

The film’s cast and crew were a nationally and ethnically diverse group, and the film’s themes of divisive British politics really hit hard during filming, when Brexit unexpectedly passed.

“Yeah, we went to bed thinking it would be one result and woke up to a shock,” Murphy remembers. “And all the actors on set would be real political animals, everyone had been following the whole campaign during it, so it was felt deeply. Sally wisely didn’t try to shoehorn it into the script after, because the film already implicitly speaks to how people were feeling at the time, and the mood and unease and paranoia that was being experienced in Britain at the time.”

Having lived in London for 14 years, Murphy has just moved back to Dublin with his wife and two sons, who are now aged eleven and nine.

“It was just time,” he muses. “It’s the Irish narrative in a way – you do a stint away and then you come home. And we’re very happy here – the kids are Irish, their grandparents are here, all these basic but important reasons always draw you back to where you come from. And I’ve said it before – Irish people are sound! I love Irish people. And I love that there’s only four million on the island. At a certain time in your life, you just want some space.”

He has passed his practical approach to the film industry onto his sons, who aren’t even that impressed that their Dad was in the Batman movies. “They’re very underwhelmed by the whole thing – as they should be, I wouldn’t want them any other way. It’s a job, and they understand that.” He hopes their cool-headedness will serve them well as they become teenagers, remarking that, “It’s such a different time – when I was their age I couldn’t even conceive of the things they have to deal with now.” When asked about his particular concerns, however, discussing his own childhood or that of his kids is “far too complicated for the time we have.”

Some borders will always remain carefully guarded.

The Party is in cinemas now.