Not all my characters are geniuses, Benedict Cumberbatch says

Benedict Cumberbatch at the 2014 Toronto International Film Festival in Toronto on Sept. 9, 2014. (THE CANADIAN PRESS / Nathan Denette)

LONDON -- "Sherlock" star Benedict Cumberbatch says his latest role as a code-breaking genius doesn't mean he's only capable of playing brainy characters.

Cumberbatch stars as computer pioneer Alan Turing in "The Imitation Game," which opens the London Film Festival on Wednesday.

Turing's work on cracking German codes helped win the Second World War, but he later committed suicide after being prosecuted for homosexuality. Now widely regarded as a wartime hero, he was granted a posthumous royal pardon last year.

"It's a great honour to be asked to play someone like Alan Turing, so the last thing I want to do is go, 'Well, it's a bit like Sherlock, isn't it,"' Cumberbatch told a news conference.

"I've also played stupid people as well," he said. "If anyone out there's got some more stupid roles for me, great, bring it on."

Keira Knightley, who plays Turing's fellow code-breaker and sometime fiancee Joan Clarke, said the actors struggled to match the problem-solving agility of their characters.

"One day we decided we should all really do the crossword," she said. "So we got the quick crossword, there were five of us. It took us five days, and we still didn't finish it."

"The Imitation Game" won the audience award at the Toronto Film Festival, often a harbinger of Academy Awards success.

It's one of 248 features playing at the 58th London festival, which opens Wednesday. It closes Oct. 19 with Brad Pitt war yarn "Fury."

Other gala screenings include Bennett Miller's wrestling drama "Foxcatcher," Mike Leigh's artist biopic "Mr. Turner" and the world premiere of "Testament of Youth," adapted from Vera Brittain's World War One memoir.

The festival will hand out prizes for best picture, best first feature, best documentary and best British newcomer at an Oct. 18 ceremony. Veteran director Stephen Frears is due to receive a lifetime achievement honour.