It's called 'Spooks: The Greater Good' and will start shooting early next year (2014)

Jennifer Ehle (above) and Kit Harington – Jon Snow in Game Of Thrones – have signed up for the forthcoming Spooks movie.

They join Peter Firth, who will be reprising his role as Sir Harry Pearce from the long-running TV show. Shooting is due to begin in the first three months of next year (2014).

Earlier this week it was revealed that the film has been given the official title Spooks: The Greater Good. Bharat Nalluri, who directed six episodes of the TV series including the first two ever and last two ever, is on board as director.

Meanwhile, the script has been written by Jonathan Brackley and Sam Vincent, who teamed up to write ten episodes of the TV series. The story will start with Firth’s Sir Harry Pearce being blamed for the escape of a terrorist and then disappearing in mysterious circumstances. With a planned terrorist attack on London looming, Pearce’s protégé Will Crombie, played by Harington, is drafted in to find out what happens and ends up tracking a conspiracy that stretches across continents.

Meanwhile, Ehle will appear as a senior MI5 figure called Dame Geraldine Maltby. One of the film’s producers Ollie Madden said in a statement: “We are delighted that Kit Harington, who blew us away as Jon Snow, will star in the lead role as Will Crombie, alongside the wonderful Jennifer Ehle as Dame Geraldine Maltby of MI5. Together with Peter Firth, who has been in this from the beginning, we’re thrilled to be bringing together such an exciting cast.”

Created by David Wolstencroft in 2002, Spooks ran for 86 episodes before ending after its tenth series in 2011. Firth was the only actor to feature in all 86 episodes but other stars who made appearances over the years included Mathew Macfadyen, Keeley Hawes, Richard Armitage, David Oyelowo, Hermione Norris and Rupert Penry Jones.