Background: Primary health care has recently undergone and is continuing to experience significant change. One issue is the increased emphasis on population health. Public health is at the centre of recent United Kingdom government policy as well as international policy. This paper describes the adoption of a specialist practitioner public health nurse role as a resource for public health practice development. The issues raised by the approach to practice and service development are located within discourses on leadership, modernisation and change in health and social care. The discussion is guided by critical theory approach to facilitate exposure of the factors influencing decisions and consequences of decisions. Evaluation method: The evaluation design drew on the theories of change approach which focuses on ‘surfacing assumptions’ underpinning a change process. Purposive sampling was used to identify a range of stakeholders to the post. Individual interviews were conducted with 11 stakeholders from management, nursing, social work and medical roles. Four focus groups were conducted with health visitors. Findings: Thematic analysis identified three issues that relate to a specialist role aimed at public health capacity development; location of the specialist role within existing teams, the routes available to providing public health subject leadership and sharing expert knowledge, potential for conflict or tensions between specialist and other roles. Conclusions: Capacity to address the public health agenda is being developed at the same time as the modernisation of leadership. The role and impact of historical organizational structures and approaches to management and leadership must be acknowledged. The research indicated that specialist posts have positive potential in relation to public health practice developments. Key success factors included involving the generalist in the rationale development of such a role, sharing expectations of the impact of all roles and where to locate the specialist role with respect to existing teams and structures.