Cillian Murphy found it a "nice challenge" to portray a 75-year-old man in movie 'In Time'.

The 35-year-old actor stars as veteran timekeeper Raymond Leon in the film, which sees his alter-ego on the trail of Will Salas - who is portrayed by Justin Timberlake - and his hostage Sylvia Weis (Amanda Seyfried).

He told "Well, it's a nice challenge. The character is actually 75. He started his career when he was 25, and he's been doing it for 50 years. So, that's a nice challenge to play, you know. And also, the character himself, he's a contradiction.

"He is enforcing a system that, I hope you can see, he fundamentally disagrees with. Yet, he has to do it to keep himself alive. So, they're all great character traits, or character notes, to try and play."

The Irish star enjoyed playing a "badass" character - and loved finally getting the chance to work with director Andrew Niccol as they had discussed a project before but it never materialised.

He added: "I'd never played that figure of authority before, that badass type guy. So, that was a departure for me."

"Andrew and myself had talked about doing a film in the past, and it didn't work out at that time. And I'm a big fan of 'Gattaca' - I think that's right up there in the science fiction genre - and, also, he wrote 'The Truman Show'."