This book examines the fraught political relationship between British governments, which wanted information about peoples’ lives, and the people who desired privacy. To do this it looks at something that Britain only experienced in wartime, a centralized and up-to-date list of everyone in the country: a population register. The abolition of this wartime system is contrasted with later attempts to reintroduce registration, and the change in the political mind-set driving these later schemes to develop centralised webs of so-called objective data is examined. These policies were confronted by privacy campaigns, studied here, but it is shown how government responses succeeded in turning political debates about data into technical discussions about computerization; thus protecting its data, largely on paper, from oversight. This reformulation also shaped the 1984 Data Protection Act, which consequently did not protect privacy but rather increased government’s ability to gain knowledge of, and hence power over, the people.