It’s 1941. Imagine you’re Winston Churchill. The Battle of the Atlantic is a disaster. Supply ships ferrying vital weapons, food and fuel from North America are being torpedoed by the German U-boats. You are lying to the country about the number of ships sunk. You are lying about the number of men killed. Without the supply ships Britain will starve. The tide of the war is turning in Germany’s favour. This is the story of the game of battleships that won the Second World War. In 1941 Prime Minster Winston Churchill gathered a group of unlikely heroes – a retired naval captain and eight brilliant young women, the youngest only 17 years old – to form a secret strategy unit. On the top floor of a ramshackle HQ in Liverpool, the Western Approaches Tactical Unit spent day and night playing war games to crack the U-boat tactics.