The Newsroom star joins the superhero franchise as Psylocke, a strong mutant with telepathic and telekinetic abilities, and she only signed on when the producers confirmed she would get a fight scene.

However, she learned that the stunt double she had been given had no previous experience, so Olivia decided to learn all the stunts herself to ensure Psylocke's fight scenes would be shot, and that they would be good enough to be included in the final cut.

"When they brought in my stunt person - she's super talented and very athletic, but she had never done stunts before, and she'd never done martial arts or any fighting, and she'd never picked up a sword," Olivia tells E! Online. "So when she told me that, I was like, 'oh, my gosh.'

"I'm like, this is Psylocke's entry into this world, I'm not (co-star) Jennifer Lawrence, if they don't have it (a good scene), they're not gonna make sure to get it in there somehow. If there's not a fight scene being shot, if they don't have it, they're not gonna use it... If I wanted the fans to see Psylocke and get a good fight scene for her and the fans, I knew I had to go do it myself."

The actress had grown up doing Taekwondo but she trained in the martial art for hours every day for the movie, while also picking up new stunt skills with swords and wire work. Her intense training regime caused her to lose 12 pounds (5 kilograms) unintentionally.

X-Men: Apocalypse opens in cinemas on 18 May (16) in the U.K. and 27 May (16) in the U.S.