Steve Carell has revealed that his creepy look for new film Foxcatcher was so effective that his castmates would distance themselves from him on set.

The American actor, best known for his comic roles in The 40-Year-Old Virgin, Anchorman and Despicable Me, donned prosthetics and heavy make-up to portray eccentric multi-millionaire and murderer John du Pont in Bennett Miller's movie.

It tells the true-life story of du Pont, whose friendship with wrestling brothers Dave and Mark Schultz, played by Mark Ruffalo and Channing Tatum respectively, ended in tragedy.

"The prosthetics influenced my performance more than I anticipated. Once all that make-up went on, people reacted and responded to me differently," he said, ahead of the film's premiere at the BFI London Film Festival.

"He did have a very specific way of talking and a certain demeanour, and he has a specific look as well. I think just his demeanour was very off-putting to many people.

"People naturally wanted to be separate from me. I was off-putting (to them). So organically I stayed in character because I didn't really have any choice - no-one wanted to talk to me."

He added: "(du Pont) got a lot under my skin, he was not easy to shake off after filming. I still talk to Channing and Mark about the experience, because it was very immersive."

Carell studied du Pont's look, speech and demeanour with video footage. He also met Dave Schultz's widow Nancy (played by Sienna Miller), their children and Mark Schultz.

The 52-year-old actor continued: "There was footage of him - he had commissioned a documentary of himself and the raw footage was most interesting. That showed a side to him that was not his public persona that he wanted to project. There was a sharper edge to that guy, and you can see little hints of it here and there."

Playing du Pont is Carell's darkest role to date, although he said it was not part of his "master plan".

"I was surprised to have been asked to meet with Bennett. But I was not actively pursuing this movie or role. It was not on my radar at the time. It was not a master plan that this dark role was something I would undertake," he added.

Director Miller, whose previous films include Moneyball and Capote, admitted he knew nothing about the story until a stranger told him.

"I never heard of this story until a stranger approached me on the street, gave me an envelope and said I should make a film about this.

"It's a mysterious story. There was not deep coverage of it and it went away pretty quickly," he said.

"I learnt about it eight years ago and committed to it immediately ... But it was hard to find support for it."

Foxcatcher, which is the Amex Gala at LFF, will be released in UK cinemas on January 9, 2015.