Actor Ezra Miller couldn't shake his shy, withered Fantastic Beasts & Where To Find Them character when he took a break from filming last Christmas (15), revealing he had become Credence Barebone.

The big screen's new The Flash felt sure he'd be able to snap in and out of the role but quickly realized his abused character was taking over his body.

"It crept up on me," he tells WENN. "I thought I had it under control and then we took a little break around Christmas time and I couldn't let parts go. There were certain physical cues...

"I talked to some people who work as professionals, responding to cases of domestic abuse and child abuse, and they said there is a common physicality, so I think instinctively his (Credence) shoulders were collapsed on his chest.

"My shoulder was stuck and I couldn't get my chest to open back up. I noticed when my mind went adrift I would suddenly start feeling very sad. There were some physical pains but well worth it. I'd do it again in a second."

Ezra reveals he perfected his look and movements with the help of ballet choreographer Wayne McGregor, who previously worked on Radiohead videos.

"He's worked with some of the various (Harry Potter) actors," the actor adds. "I think he worked with Ralph Fiennes on developing Voldemort's wand language."