Alice Roberts explores the Second World War history of Dover, visiting an underground base beneath the famous white cliffs, from where the Dunkirk evacuation was masterminded. She also talks gets a first-hand account of the town's wartime history from a 90-year-old local and experiences what life was like for members of the Auxiliary Territorial Service during the Battle of Britain. Plus, aerial archaeologist Ben Robinson takes to the sky to survey the challenges faced by Royal Navy vessels deployed in the English Channel