Cillian Murphy has said that he needed to be pretty ‘unhealthy’ to really get into filming Oppenheimer, and it’s affected the way that he might think when selecting future roles.

The Irish actor plays scientist J. Robert Oppenheimer in Christopher Nolan’s latest movie, and had to make some sacrifices to get into the character of the ‘father of the atomic bomb’.

Oppenheimer was a theoretical physicist who became best known for his contribution to the Manhattan Project, which was a research and development project that took place in the USA during World War Two and led to the creation of the first atomic bombs.

Those bombs later resulted in the destruction of Hiroshima and Nagasaki in Japan, which – whilst arguable hastening the end of the war – also killed hundreds of thousands of people and destroyed countless lives afterwards.

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To this day, the bombs created by Oppenheimer and his colleagues remain the only nuclear weapons to be used in armed conflict.

Anyway, to inhabit the fascinating role, Murphy had to make a number of personal sacrifices, including getting into the titular character’s chain-smoking habit.

Of course, he was smoking fake cigarettes and a fake pipe, but even the prop cigarettes can contain harmful stuff, and he clearly didn’t feel well afterwards.

Murphy is no stranger to a fake cigarette, as his years as Thomas Shelby in Peaky Blinders saw him consume hundreds of the things.

Universal Pictures

However, this time around he’s looking for a role that doesn’t require him to be puffing away on something non-stop.

The 47-year-old said he’s been turned off ‘fake cigarettes’ entirely, adding: “Cigarettes and pipes. He would alternate between the two. That’s what [killed] him in the end.

“I’ve smoked so many fake cigarettes for Peaky and this,” he told The Guardian. “My next character won’t be a smoker.

"They can’t be good for you.”

And it wasn’t just the fake smoke that was getting to him.

The actor also had to lose quite a bit of weight in order to appear physically more like the skinny scientist.

Apparently, that wasn’t something he enjoyed, either.

Universal Pictures

“You become competitive with yourself a little bit which is not healthy,” he said. “I don’t advise it.”

To be fair, most doctors probably wouldn’t, either.

Oppenheimer features a big ensemble cast that – as well as Murphy – includes Florence Pugh, Emily Blunt, Matt Damon, Robert Downey Jr., Josh Hartnett, Casey Affleck, Rami Malek, and Kenneth Branagh.

It will be released in cinemas on July 21, the same day as Greta Gerwig’s Barbie, starring Margot Robbie and Ryan Gosling.

Maybe just see what kind of mood you’re in when you wake up that morning, eh?