The first major reorganisation of the National Health Service took place in 1974, twenty-six years after the service had been established. It has long been perceived as a failure. This article draws on archival records and a witness seminar held in November 2016 to provide a more nuanced assessment of the 1974 reorganisation and understand more fully why it took the form that it did. In particular it identifies the reorganisation as an important moment in the ongoing story of management consultants engaging with health policymakers, and explores the role of McKinsey and Co. in detail for the first time. Key explanatory factors for their involvement are identified, including the perceived lack of expertise and manpower inside the civil service and the NHS, and perceptions of their impact and effectiveness are discussed. Many debates about the use of management consultants today were directly foreshadowed during the early 1970s. Alongside this, the role of other groups of policy actors, including civil servants, politicians and medical professionals, are established and the extent to which British health policymakers have had to work within existing cultural, political, legislative and practical constraints when trying to initiate change is demonstrated. The fact that many of the 'mistakes' that were made have been repeated in the course of subsequent reforms, speaks to the poor institutional memory of Whitehall, and the Department of Health and Social Care in particular. In the run up to 1974 management consultants could make only a limited contribution to an imperfect compromise.