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Harrison Ford, Anthony Hopkins, Natalie Dormer, Paul Bettany, and Martin Freeman will star in the spy thriller Official Secrets, the Solution Entertainment Group announced Thursday.

Based on Marcia Mitchell’s nonfiction book The Spy Who Tried To Stop A War, the film is to recount the story of Katharine Gun, a British intelligence officer who leaked information to the press about an NSA spy operation allegedly intended to press the U.N. Security Council into sanctioning the Iraq invasion.

Dormer will portray Gun, Bettany and Freeman will play journalists at the London Observer, Hopkins will play a retired U.K. general, and Ford will portray a CIA agent.

Justin Chadwick (Mandela: Long Walk to Freedom, The Other Boleyn Girl) is directing from a script by Sara Bernstein and Gregory Bernstein. Elizabeth Fowler is producing, with Lisa Wilson and Myles Nestel executive producing.

Production is scheduled to start in the U.K. in May.