This book traces the emergence and development of the relationship between management consultancies and the British state. It seeks to answer three questions: why were management consultants brought into the machinery of the state; how has state power been impacted by bringing profit-seeking actors into the machinery of the state; and how has the nature of management consultancy changed over time? The book demonstrates the role consultants played in major developments in the postwar period. Specific case studies interrogate how consultancies influenced the policy fields of health service reform and social security benefits. This book will redefine debates amongst business historians and historians of the postwar British state about the nature of management consultancy and public sector reform.