Millions of words have been spent and misspent on Adolf Hitler. But there remains one aspect as yet insufficiently explored: the impact of the First World War on the man who would go on to indelibly shape the Second.

Hitler fought at First Ypres and he saw something on the battlefields that eluded his fellow soldiers, something that would become the cornerstone of his later life. He saw this war as heroic, noble and natural - the last act of the fittest in the great drama of the human race.

Where did it all start? This is the story of how Hitler became the Fuhrer.