In the 1920s, Imperial Britannia was sliding from view and a more modern Britain tried everything new and asked endless questions about how we should live our lives. A great new age of experiment arrived in politics, writing, art, sex and drugs. Survivors of World War I threw themselves into the new urban scene of nightclubs, cocktails and jazz, where royalty, gangsters and Hollywood stars rubbed shoulders with new money.

For Andrew Marr, the story of Britain in the 1930s was one of betrayal, political extremism, unemployment and... hats. Bowlers, trilbies, top hats and flat caps were everywhere, as the country descended into chaos when the financial crash on Wall Street engulfed Britain. Solutions to the national crisis were offered by Britain's most unlikely paramilitaries, the Greenshirts.

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.

In the first of a six-part series, Andrew Marr revisits Britain at the dawn of the 20th century. He finds the country mourning the death of Queen Victoria; fighting an intractable war against the Boers in South Africa; enjoying the bawdy pleasures of music hall; and worrying about the physical and moral strength of the working class.

The assassination of an archduke in Sarajevo sets in motion the wheels of world war. In the corridors of Westminster old allies Winston Churchill and David Lloyd George fight over strategy. Out on the streets, the people are eager for battle, determined to 'teach the Hun a lesson'. Britain is on the road to war.

Britain gets its first taste of total war. Marr argues that no shock has ever hit these islands with quite the force of what became known as the Great War. It transformed the lives of the British people - most dramatically the millions who fought on the frontline but also those at home who were bereaved, bombed, uprooted and bankrupted.