This paper reports on a study of teacher educators preparing teachers for the Further Education and Skills sector in England. Thirty-six teacher educators participated in an intervention intended to enhance understanding of subject-specialist pedagogy. Based on a socially-situated conception of pedagogical content knowledge, the intervention included a workshop supplemented by specially-developed learning resources. Data on prior knowledge, initial reception, and longer-term impact was collected by pre-intervention survey and at least one post-intervention interview. The paper explores how the intervention impacted participants’ understanding and practice, and proposes a typology for understanding the longer-term sustainability of this impact.