Across the world, organisations and public systems are under strain - facing rising demand, constrained resources and reforms that seldom deliver lasting improvement. 'One System' tells the inside story of a rare exception. Over more than a decade, Canterbury radically reimagined how its health system could work. The aim was simple: to act as one system, organised around people rather than institutions. This new way of working was tested under the most difficult conditions: the Canterbury earthquakes, the Christchurch Mosque attacks and the COVID-19 pandemic. Written by two of those who led the work, 'One System' offers a candid and practical account of enabling transformation in real conditions, under constant pressure and without the illusion of a perfect master plan. Grounded in health care but relevant far beyond it, 'One System' is for leaders, clinicians, governors, policymakers and anyone grappling with change in a complex system.