This study of leadership in the British civil service draws the lessons of how change in central government can be managed and implemented from a series of biographical studies of the acknowledged leaders in the civil service in the 19th and 20th centuries, from Charles Trevelyan, the founder of the modern civil service, to modern Mandarins such as Robert Armstrong and Margaret Thatcher’s personal adviser the outsider Sir Derek Rayner. The case studies are linked to the wider themes of leadership and administrative culture in Whitehall, illustrating the patterns of change and continuity over time.