Trance actor James McAvoy admitted that he sometimes finds himself cast in roles where he ''doesn't know what'' he's going to do after reading the script.

The 34-year-old actor explained that he can't always envision a part just by reading the script, but he gets a great feeling when one immediately leaps out at him, such as his current film, Filth.

ContactMusic quote the star as saying: ''Sometimes when you read a script you don't start getting ideas and that can be slightly worrying. I have done jobs where I think, 'I don't know what the **** I'm going to do,' and you just get there on the day and make it work. But with Filth every single scene just presented so many ideas and I was inspired immediately.''

James further explained that he knows his name can help films gain backing, but he trusted Filth director Jon S. Baird as soon as he met him, saying:  ''Sometimes filmmakers want you just because they think you can help get things financed. [But] sometimes you just get a feeling and I trusted Jon. He is very strong, very bold and very direct, *******t is not part of his makeup. So I thought, 'He's definitely the guy to direct this because you need someone brave and bold.''