This book traces the development of policy and the regulatory framework for the commercial nuclear power industry in the United Kingdom between 1945 and 2005. It is argued that throughout the whole period politicians have legitimised their decisions in terms of a scientific discourse that represents the scientific community as unified and the decisions as thus self-evident. In each of four distinct time periods the key policy developments and legislative initiatives were based on pragmatic considerations. A distinction is made between two types of pragmatic considerations – reactive and proactive. While these types overlap in practice, in some cases the decisions were predominantly reactive and taken in relation to emergencies and global forces, and in others the decisions were predominantly proactive attempts to ensure a suitably balanced and priced energy mix.