Filmed at the Royal Geographical Society on 15th April 2014. The First World War is not called the Great War for nothing. It was the single most decisive event in modern history, as well as one of the bloodiest: by the time the war ended, some nine million soldiers had been killed. It was also a historical full stop, marking the definitive end of the Victorian era and the advent of a new age of uncertainty. By 1918, the old order had fallen: the Bolsheviks had seized power in Russia; the German, Austro-Hungarian and Ottoman empires had been destroyed; and even the victorious Allied powers had suffered devastating losses. It was supposed to be the war to end all wars. And yet barely two decades later, the world was again plunged into conflict. Little wonder then that historians still cannot agree whether Britain’s engagement was worth it.