A mother of three living in a small British village, and an accomplished Soviet operative who co-ordinated a network of spies within Britain's atomic weapons programme. In this episode, Ben Macintyre joins Dan Snow to discuss one of the greatest spies of the 20th century, the woman alternately known as Mrs Burton, Agent Sonya and, her real name, Ursula Kuczynski. See acast.com/privacy for privacy and opt-out information.