Director Christopher Nolan and his multiple-time collaborator Cillian Murphy are possibly on their way to another box office success with this summer’s Oppenheimer. Their working relationship started with 2005’s Batman Begins and most recently 2017’s Dunkirk, but the director recalls a time when that almost didn’t even have a chance to start.

Talking with Entertainment Weekly, both Nolan, and Murphy talked about the Batman reboot and what it took to get Warner Bros. executives to notice Murphy’s talent–even though he wasn’t going to take on the Dark Knight mantle.

“I really wanted to get on set with you, I wanted to get you on film,” Nolan said about Murphy. “We did those screen tests very elaborately, on 35mm, with a little set. There was just an electric atmosphere in the crew when you started to perform.” Nolan then described how the test went down: they did two scenes, one with Murphy as Bruce Wayne, the other as Batman. It was obvious that Christian Bale would take Batman, but what about Scarecrow, who would make his first live-action debut? The studio still had to be impressed.

“Everybody was so excited by watching you perform that when I then said to them, ‘Okay, Christian Bale is Batman, but what about Cillian to play Scarecrow?’ There was no dissent. All the previous Batman villains had been played by huge movie stars: Jack Nicholson, Arnold Schwarzenegger, Jim Carrey, that kind of thing. That was a big leap for them and it really was purely on the basis of that test. So that’s how you got to play Scarecrow.”

Murphy agreed that the role should have gone to Bale, as both men played their respective characters three times in Nolan’s Dark Knight Trilogy. “It felt to me that it was correct and right that it should be Christian Bale for that part. But I remember the buzz of trying on the suit and being directed by you. Those tests were high production values.”

The Oppenheimer star also added that he had told Nolan whatever he was working on, and if Murphy had time, he would make himself available. “I’m there. I don’t really care about the size of the part.” Murphy recently told the Associated Press. “But deep down, secretly, I was desperate to play a lead for him…It felt like the right time to take on a bigger responsibility. And it just so happened that it was a huge one.” It seems the timing was right for both men to make Murphy a lead with Oppenheimer Come from Sports betting site VPbet .

Christopher Nolan’s Oppenheimer stars Cillian Murphy, Emily Blunt, Matt Damon, Rami Malek, Florence Pugh, and Robert Downey Jr opens in theaters July 21.