"A picture of the London front" represents Britain's earliest experiences of war in 1939.
An introduction, showing children playing on captured German guns and the Imperial War Museum, recalls "20 years" since WW1. The superficial normality of Sunday September 3 is interrupted by Chamberlain's announcement of war and the first air-raid alarm (reconstruction). These early days of war bring "remarkable things": Londoners of all classes cooperate in preparing sandbag defences; the anti-militarist inter-war generation goes into military training. Much London life continues with superficial adjustments (ARP, reserve police etc) but hospitals, children, pets and art treasures are evacuated (the National Gallery and the British Museum), and more obvious signs of war appear (balloon barrage, army training and equipment, women in uniform); foreigners registered; the soldiers depart. A sequence implies the continuation of war (AA defences; aircraft and munitions production; hospitals etc) through the night and on into the next day, and the film ends on a confident note: "This is not twilight that has come to England: it is dawn, and dawn we hope, for more than England... The London Front still stands."