Against a backdrop of a transformation in teacher professional development and learning and state school organisation in England this century, this chapter describes a project which harnessed six cycles of Research Lesson Study at school and district level over two years to tailor the implementation of a new statutory curriculum in England to address the professional development needs of teachers and classroom learning needs of London students. It also reports the findings of research carried out during the project into how these teachers learned and developed this new curricular expertise and practice- knowledge through lesson study dialogues that supported student learning. It concludes by proposing future directions for teacher professional learning research and practice.