Within education there has been considerable research into the process of learning to teach. This has often taken the form of investigations of trainee-teachers' knowledge and beliefs. However, within ELT, empirical research into the development of trainees' thinking whilst taking a formal training programme is limited. This article reports on a case study of a pre-service (CELTA) course and takes as its focus an in-depth look at the development of one trainee. The trainee, Penny, despite her "ab-initio" status, held strong beliefs about teaching which interacted with her experience of the training programme in sometimes complex ways. Whilst some of her pre-course beliefs showed elaboration and a deepening understanding, others were remarkably resistant to change. One particular area where she did evidence a growth in her understanding, was in the shift of her perspective on grammar from that of a learner to that of a teacher.