It is clear that the era of unprecedented investment in health care is over, and prospects for future funding now look bleak. But just how the NHS will respond to this is uncertain. To test how those in the system might respond, we used a behavioural simulation – Windmill 2009, designed by Loop2. From this event, and discussions with policy-makers, regulators, commissioners and providers, managers and clinicians, we developed an analysis of what will be required if health and social care systems are to respond effectively to the major challenges that lie ahead. We identify key themes and recommendations for action in each of these.