You wouldn't normally expect hundreds of screaming fans to turn out for the premiere of a British period drama on a wet and windy night.

But that's exactly what Benedict Cumberbatch was faced with when he and Keira Knightley walked the red carpet at the European opening of The Imitation Game - their new movie about the life and work of computing pioneer Alan Turing.

Sherlock star Cumberbatch has already been tipped for an Oscars nomination for his role as Turing - who helped crack a German communication code, giving the Allies a big advantage at the end of World War Two, but was later persecuted for his homosexuality.

And he was reverential when discussing the film's subject, telling the BBC: "To be asked to play such a phenomenal human being - a true English hero - is a great honour and comes with a great responsibility."

Admitting that he had been ignorant of Turing's life and work before the film, he added: "That's the tragedy of this man's extraordinary life - his achievements and his heroism and his criminal prosecution are not well known.

"He should be on the front cover of text books."

The premiere also marked the start of the BFI London Film Festival - and while Cumberbatch looked dapper in a simple dark jacket, white shirt and dark tie, his co-star Knightley stunned fans and photographers in an elegant, layered gold dress.

The Imitation Game is released in UK cinemas on 14 November.