OBJECTIVE: Little is known about how to achieve scale and spread beyond the early local adoption of an innovative health care programme. We use the New Care Model - or 'Vanguard' - programme in the English National Health Service to illuminate the process, assessing why only one of five Vanguard programmes was successfully scaled up. METHODS: We interviewed a wide range of stakeholders involved in the Vanguard programme, including programme leads, provider organisations, and policymakers. We also consulted relevant documentation. RESULTS: A lack of direction near the end of the Vanguard programme, a lack of ongoing resources, and limited success in providing real-time monitoring and evaluation may all have contributed to the failure to scale and spread most of the Vanguard models. CONCLUSIONS: This programme is an example of the 'scale and spread paradox', in which localism was a key factor influencing the successful implementation of the Vanguards but ultimately limited their scale and spread.