Mark Strong has apparently joined The Imitation Game, the film about Enigma codebreaker Alan Turing.
Sherlock star Benedict is already signed on to portray the brilliant British mathematician and cryptographer, who helped crack the German enigma code during the final years of World War II. He was later prosecuted by the government for being a homosexual and committed suicide.
Keira has been in talks to play a woman from a very conservative background who formed a complicated relationship with Turing and was a close friend to him up until his death.
Matthew Goode, Charles Dance, Downton Abbey's Allen Leech and Matthew Beard will also have roles in the film, which is being directed by Norwegian filmmaker Morten Tyldum and is based on Andrew Hodges' book Alan Turing: The Enigma.
The movie, which has been written by Graham Moore, was top of the film's industry Black List of hotly tipped unproduced scripts in 2011. Leonardo DiCaprio was previously linked to the role of Turing, while Ron Howard was said to be interested in directing it.
The Imitation Game is due to start shooting in coming days, for a release in 2014.