This paper discusses the methodology and main findings of a formative evaluation of aspects of the London Leadership Strategy (LLS). The LLS is an ambitious example of a programme designed and supported by the National College of School Leadership in England (NCSL) to enhance leadership and management so as to improve the quality of education and raise standards in London schools. This paper focuses on the Consultant Leader programme and the cumulative impact of involvement in multiple strands of the LLS programme. The research adopts a mixed methods strategy to identify the experience and impact of the Consultant Leader programme on the quality of life of staff and achievements of pupils in the 400 schools. It combines quantitative data about pupil attainment and progress and evidence on standards and processes drawn from school inspection reports published by the Office for Standards in Education (Ofsted) with qualitative case study data about engagement in different aspects of the LLS. These case studies explore stakeholders’ perceptions of the impact of LLS activity in their schools. The research identified a number of key factors which contributed to the relative success of the various programmes. These will be relevant particularly to leaders in low socioeconomic schools.