Cillian Murphy on Oppenheimer, sex scenes and self-doubt: ‘I’m stubborn and lacking in confidence – a terrible combination’

Cillian Murphy is struggling with what he can and can’t say about his title role in Oppenheimer, the latest Christopher Nolan epic, such is the secrecy surrounding this film. Murphy is under “strict instructions” not to talk about the content. Which is awkward when you’ve flown to his home in Ireland to interview him specifically about playing the physicist who oversaw the creation of the atomic bomb, later detonated over Hiroshima and Nagasaki. It’s not clear who issued these instructions. Nolan? The studio? The US government? All I know is that as well as Murphy being gagged by hefty NDAs, I am not allowed to see it (“bit unfortunate”, he concedes).

So, yes, here we sit in an empty upstairs room of a restaurant near his house in Monkstown, Dublin, working out how to do this. The room is dark, the sun shining through a solitary Velux lighting his features like a Géricault. The only background noise is the low hum of a wine refrigerator. Murphy loathes interviews, looks visibly tortured at points. But he relaxes when I ask if he’s pleased with Oppenheimer. “I am, yeah,” he says. “I don’t like watching myself – it’s like, ‘Oh, fucking hell’ – but it’s an extraordinary piece of work. Very provocative and powerful. It feels sometimes like a biopic, sometimes like a thriller, sometimes like a horror. It’s going to knock people out,” he adds. “What [Nolan] does with film, it fucks you up a little bit.”

Nolan wouldn’t disagree. The director recently that some of those who’d seen it were left “absolutely devastated … they can’t speak”. Which sounds like a bad thing, but is related perhaps to the thought of the 214,000 Japanese people, overwhelmingly civilians, who lost their lives when the bombs were dropped. Kai Bird, the historian who co-authored American Prometheus, the upon which the film is based, said he was