Sherlock star Andrew Scott will play a Soviet spy in a new one-off Cold War drama with Romola Garai and Simon Russell Beale.

Legacy stars Boardwalk Empire actor Charlie Cox as British spy Charles Thoroughgood, who is forced to confront the possibility his own father might have been a double agent.

The 90-minute programme is based on the novel of the same name by Alan Judd and has been adapted for television by award-winning writer Paula Milne.

She said: "Legacy falls well within the genre of the British spy thriller but has an extraordinary personal twist. For what is espionage if not betrayal at the most fundamental level of human interactions? When that occurs within a family it's dynamite."

Andrew, who starred as criminal genius Moriarty in the BBC's revamped version of Sherlock, plays a Russian diplomat while Russell plays a British spymaster.