In this chapter I take up the idea of mathematics teacher education as a subversive activity – not necessarily in the revolutionary mode envisioned by Postman and Weingartner in their classic book, Teaching as a subversive activity, but as a way of finding spaces for innovation and agency. This is how I have come to think about developing expertise as a mathematics teacher and mathematics teacher educator. These two phases of my professional life are closely intertwined, with the opportunities I enjoyed as a mathematics teacher later influencing my values and goals as a mathematics teacher educator. For this reason, the chapter is organised to follow my trajectory from teacher to teacher educator to understand how I became who I am.