Kit Harington and Jennifer Ehle have signed on for the Spooks movie.

The pair will join original star Peter Firth for the big screen adaptation of the popular UK spy series, Digital Spy reveals citing The Hollywood Reporter.

Bharat Nalluri will also return to direct the film, which will be titled Spooks: The Greater Good.

The film centres around an MI5 agent (Harington) who is investigating the escape of a terrorist during a routine handover. He must solve the mystery in the face of an imminent terror attack on London.

Harington stars as Jon Snow in HBO's Game of Thrones.

Ehle is best known for her 1995 BAFTA-winning performance in the BBC's Pride and Prejudice.