Oppenheimer star Cillian Murphy avoided cast dinners because his brain was 'too full'

Cillian Murphy may have avoided attending cast dinners while shooting Christopher Nolan's new drama Oppenheimer in New Mexico, but the Irish actor's decision indicated no lack of friendliness on his part. According to costars Emily Blunt and Matt Damon, Murphy simply had too much on his mind portraying physicist and "father of the atomic bomb" J. Robert Oppenheimer to socialize with his castmates.

"The sheer volume of what he had to take on and shoulder is so monumental," Blunt said in a new interview with PEOPLE. "Of course he didn't want to come and have dinner with us."

According to Damon, Murphy "couldn't" join them for meals: "His brain was just too full."

Based on the 2005 book American Prometheus and set for release July 21, Oppenheimer is billed as an "epic thriller that thrusts audiences into the pulse-pounding paradox of the enigmatic man who must risk destroying the world in order to save it."

Melinda Sue Gordon/Universal Pictures Matt Damon and Cillian Murphy in 'Oppenheimer'

Murphy himself previously spoke to EW about the excitement he felt being offered the lead role by Nolan. The actor has taken supporting roles in five of the director's films: 2005's Batman Begins, 2008's The Dark Knight, 2010's Inception, 2012's The Dark Knight Rises, and 2017's Dunkirk.

"It was one of the best days of my life, I'll tell you that," Murphy said. "I'll always turn up for Chris, no matter what the part is, but, secretly, it's a dream to play a lead part. The thing was, I had no idea. There was no preamble or anything, I just got the call. So it was incredibly exciting, and daunting, and terrifying, all at the same time."

The actor also spoke about being part of the film's starry cast, which includes Robert Downey Jr., Florence Pugh, Rami Malek, Josh Hartnett, and Kenneth Branagh.

"Every day, you had these phenomenal actors, who are heroes of mine, coming in," he said. "Every day, you were having to raise your game to work with these legends. Everybody was so unbelievably well-prepared. Every single actor, no matter what size their role or the significance of their character in history, each one of them had this massive depth of knowledge that they could draw on."

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