Marr's story of 'the people's war' begins with the defeat that came to define modern Britain's national spirit: Dunkirk. In 1940, Britain stood alone against the might of the German war machine. Churchill produced the words that stirred the Blitz spirit, but a Nazi invasion seemed inevitable. How could Britain fight on? The 'Dad's Army' of the Home Guard was hastily assembled and Britain was forced to pull together in ways it never had before.

• Andrew Marr