The story of the first 25 years of Australia's national signals intelligence organisation, told for the first time. At the end of World War II, it was clear that the nation must never again find itself entering a major war without a national intelligence capability. The Factory tells the story of how Australia's talented signals intelligence amateurs took an ad-hoc wartime organisation and made it a national agency that became a highly regarded member of the 'five eyes' signals intelligence system. Founded in 1947 as the Defence Signals Branch, the organisation built upon the foundations put in place by the interwar Royal Australian Navy and wartime signals intelligence agencies, particularly Central Bureau Brisbane, which comprised personnel from all five eyes nations. Today's Australian Signals Directorate continues the work of protecting the interests of the nation and its allies. This is the story of the people who did the everyday work of capturing and analysing foreign signals. It reveals how they approached the complexity of world politics and managed massive technological change, from the days of radio transmissions to high-capacity machine systems and computing during the Vietnam War.