On 29 December 1940 London experienced one of its worst nights of the Blitz. German bombers dropped tens of thousands of bombs, destroying more of London than the city's famous Great Fire of 1666. The following morning, a photographer took a picture through the smoke and fire of Saint Paul’s Cathedral. One of the most famous photos ever taken. A symbol of hope in the midst of the Blitz. Dan Snow goes on a tour around the City of London with historian Clive Harris to learn more about what happened that infamous night 80 years ago. About the heroes who bravely tackled this man made inferno.