In this paper two premises are set out: first, that within Children's Services educational psychologists (EPs) have a distinctive contribution to make towards policy and practice in relation to "dyslexia"; second, that they may be well placed to lead development work at an organisational level within a local authority. Building on previously unpublished work, the authors report a case study of the development of a local authority dyslexia policy led by an EP over a two year period. Data were collected from an account by the lead EP, a policy development group members' focus group, and a questionnaire survey of special educational needs coordinators (SENCos). The findings confirm the scientist-practitioner contribution of the lead EP to both the product and the process of successful policy development and implementation. Facilitators, barriers and secondary benefits in relation to successful policy development within multi-disciplinary Children's Services are considered, and the policy-practice inter-relationship is theorised.