If you’re an up and coming British actor who wants to get movie roles, you need get cast in either Downton Abbey or Game Of Thrones. Now another of Downton’s stars is moving to the big screen as Variety reports that Allen Leech – aka’s the Abbey’s Tom Branson – has signed up to appear in The Imitation Game.

The film is a biopic of famed codebreaker and father of computers Alan Turing, with Benedict Cumberbatch set for the lead role. Turing is best known for helping the Allies defeat the Germans in World War II by breaking codes and building machines that were the forerunners of modern computers (which were based on his theories). However, in the 1950s he was prosecuted by the British government for being gay.

Turing made the extreme decision to undergo chemical castration instead of going to prison. In 1954 he died from cyanide poisoning, with many believing he killed himself by dosing an apple with the substance (although there are still some who believe it was accidental).

Leech will apparently play a Scottish spy for the Soviets who plots against Cumberbatch’s character. There’s no news on exactly how the spy will fit into the movie.

There’s already some controversy about the film, with the man who wrote the biography it’s based on, Andrew Hodges, saying he’s, “alarmed by the inaccuracies in it”, most notably the fact they have turned fellow code breaker Joan Clarke (Keira Knightley) into a “complicated love interest”, with Hodges saying “They have built up the relationship with Joan much more than it actually was.”

He’s also concerned about a central romance with  John Cairncross, who was later identified as the fifth man in the British spy ring that included Kim Philby and Guy Burgess. Hodges has said, “Their relationship is invented”.

However the producers have said that while they’ve taken the creative liberties the screenwriter is still being worked on and they want to get it right.

Morten Tyldum is set to direct the movie.