Teacher education is a complex policy and practice landscape and teacher educator roles are changing. This thesis investigates variation in how teacher educators in England account for their practices within initial teacher education, in the context of secondary mathematics. It sets out a view of their experiences of teacher education in relation to different ways of accounting for relations between knowledge about teaching and learning mathematics and knowledge of mathematics. Outcomes are based on interviews with sixteen participants, including both school-based and university-based teacher educators. Teacher educator accounts comprised four, hierarchically inclusive descriptions of learning in teacher education: (1) understanding teaching and learning in mathematics (2) linking teaching and learning with the subject discipline of mathematics (3) integrating teaching and learning with the subject discipline of mathematics (4) reconceptualisation of teaching and learning with mathematics. Accounts of teacher education are structured as expanding opportunities for student teachers to engage critically with the process of reconceptualising mathematical knowledge into ‘school maths’ knowledge. The most developed accounts position teacher education as drawing on opportunities for student teachers to experience interplay between mathematics and school mathematics through advanced and multiple mathematics perspectives. This interplay is a site of learning in teacher education. Participants hold a range of teacher educator roles, including school-based and university-based roles. Teacher educators in school-led roles were less able to draw on this interplay in practice and so this thesis is a further and timely contribution to the research about university-based teacher educators. This thesis contributes a curriculum forms perspective that focuses on teacher educator positions on the role of the curriculum in developing new teachers.