Edward Norton insisted on having his hair in perfect cornrows for his latest role.

The US actor wanted to accurately portray a prisoner in his latest thriller, 'Stone', and went to great lengths to find a hairdresser who could style his hair in perfect cornrows - small braided knots of hair in lines across his head, which are easy to maintain and popular with inmates.

Edward told website flicksandbits.com: "First off the cornrows were real. But there weren't any hairstylists in Hollywood who could do cornrows properly, so we found a lady called Crystal from Detroit who does a nice clean set of rows."

'The Incredible Hulk' actor- who plays an arsonist who is trying to manipulate his parole officer, portrayed by Robert DeNiro, in the thriller - said the radical style change was a big hit with the film's director John Curran.

He explained: "I said things to him like 'I'm seeing a lot of these convicts in cornrows and things.' I think he was like, 'What?'

"One of the big thrills to me was the first day we really started working on it, he came around the corner from the camera and his eyes were really wide as he saw my hair and he just came over and went, 'I just love this. I love where you're going with this."

Edward, 41, added he really enjoyed researching his role, because it gave him time to find out more about how convicts act and behave.

He said: "Just the couple weeks I got to sit around in this prison and talk to these guys who are incarcerated, it was a revelation for me, it was a hugely memorable experience. I love that part every time."

'Stone' - which also stars Mila Jovovich - will be released on October 8 in the US.