EXCLUSIVE: Tom Hughes, who plays Prince Albert in ITV/Masterpiece’s Victoria, is joining the cast of Red Joan, the story of a grandmother exposed as the KGB’s longest-serving British spy. Based on the 2013 book by Jennie Rooney, it’s inspired by real-life events. Judi Dench is playing the eponymous Joan Stanley with Sophie Cookson (Kingsman: The Golden Circle) as the young Joan. Trevor Nunn is directing from Lindsay Shapero’s script.

The film takes place in two eras. In a picturesque village in England, Joan Stanley lives in contented retirement, hiding her incredible past as one of the most influential spies in living history. Suddenly her tranquil existence is shattered as she’s shockingly arrested by MI5.

Flashback to Stanley as a 1930s Cambridge physics student who falls in love with seductively attractive Russian saboteur, Leo (Hughes). Through him, she begins to see that the world is on a knife-edge and perhaps must be saved from itself in the race to military supremacy.

After the war, she works at a top-secret nuclear research facility and is confronted with the impossible: Would you betray your country and your loved ones if it meant saving them? What price would you pay for peace?

Embankment is selling the project that’s produced by David Parfitt and exec produced by Ivan Mactaggart. Hughes is repped by UTA and Gordon & French in the UK.