Gerard Butler on his role for 'Copshop'

Speaking to HeyUGuys.com, he said: "I wouldn't call it talent, but it's definitely natural. I definitely have that - you know, that movie I made, 'The Vanishing', in Scotland a couple of years ago. It was interesting, delving into every part of that madness - I thought, 'S***, this is all me'.

"I have all this in me, I have light, I have a lot of darkness. So with Viddick, it was the same idea, tapping into that crazy part of you, that part that could kill somebody, or could be unleashed."

The 51-year-old actor also pointed to the importance of "having fun" on screen, even when it comes to the darker roles, reports femalefirst.co.uk.

He added: "And then also having fun with it - that moment when I scream... You climb into the mind of a killer or a hitman, and try to take that as seriously and truthfully as possibly. But then also you go, how can I make this fun, and shocking, and interesting, and different colours and layers?"

On the subject of keeping things fun, Butler also joked he'd be able to step into a 'Mamma Mia' sequel in place of Meryl Streep.

He quipped: "Yeah, maybe 'Mamma Mia' would be a good one! I don't know if I can still sing, I gotta work on my voice cords again, get them back in order. I do think I could probably do a better job than Meryl in 'Mamma Mia'."