Downton Abbey star Allen Leech has become the latest cast member to be lured by Hollywood after landing a role in a major movie.

The actor, who plays Tom Branson in the ITV show, will appear alongside Benedict Cumberbatch and Keira Knightley in wartime thriller The Invitation Game.

The film stars Benedict as Alan Turing, the maths genius who managed to crack the Enigma code during World War II.

“Downton was a dream come true for Allen but getting a part in a Hollywood film is out of this world,” a source told the Sunday Mirror.

“He is a massive fan of Keira and Benedict and he starts filming in September. It’s going to be a very interesting film about the life of Alan Turing – a ­subject which Allen is very interested in.”

No further details of the actor’s role in the film – due for release in 2014 – were confirmed.

Allen will also return as Branson in the fourth series of Downton Abbey which begins on ITV this autumn.

His character is set to find love again following the tragic death of his wife Lady Sybil (Jessica Brown Findlay) in childbirth.