Katy Long tells the extraordinary story of what Bertolt Brecht called 'the most distinguished part of man's anatomy': the passport. Katy shows how out of step today's modern, biometric, highly securitized and nationalized idea of a passport is with the document's origins, and how it came to be this way. She reveals a document which was once merely to demonstrate personal identity, how in the 18th century many British citizens travelled on French passports because they were cheaper; while after the French revolution, French citizens were often issued British passports. Not only were passports personal, and optional, but Katy shows how they were also intended to be temporary, and how Britain was the greatest opponent of the system. As so often, it was the First World War which changed everything, and Katy travels to Geneva to the archives of the League of Nations which, tasked with abolishing passports, instead laid down the rules for a new international passport system which still largely operates today. Producer: Giles Edwards.