In 15 September 1940, the Luftwaffe made a gigantic aerial assault on London in the belief that the Royal Air Force was down to its last few fighters. They had hoped to finish the RAF and force Britain to the negotiating table, but this was not to be the case. In this episode, Dan is at Bentley Priory, the HQ of RAF Fighter Command, with historian Stephen Bungay. Stephen describes how a combination of technology, leadership, bravery and organisation helped Britain to win the battle for its shores.