Georgina is joined by Calder Walton, a historian of intelligence and global security at Harvard University’s Kennedy School of Government. He is a world-leading expert in intelligence history, great-power conflict, espionage and grand strategy. He also regularly contributes to the ‘BBC’, ‘Foreign Policy’ and ‘The Washington Post’. His new book ‘Spies: The Epic Intelligence War Between East and West’, builds on secret archives and exclusive interviews with former agents to tell the story of the century-long secret war between Russia and the West.