Scottish actor James McAvoy relished preparing for his role in new movie Filth as it meant he was able to over-indulge in his favourite fattening snack - his grandmother's bacon sandwiches.

The Wanted actor has been cast as overweight, sleazy policeman Bruce Robertson in the film based, on Irvine Welsh's 1998 novel of the same name, and he threw himself into a programme of eating unhealthy foods and shunning exercise to gain weight for the shoot.

Director Jon S. Baird tells Britain's Daily Record, "James is normally a very healthy guy but he purposefully slackened off the diet and fitness to beef up a bit. We didn't want his character to be a massive fat guy, but he had to look pasty and untoned (sic) and James knew exactly how to go about that.

"While we were in pre-production, I came up to his grandmother's house... and watched him eat four bacon sandwiches. Then he looked at me and said, 'I'm going for it you know.'"