This article presents an independent evaluation of the Action Research for Physics (ARP) programme, a nationwide professional development programme which trains teachers to use action research to increase student interest in physics and encourage them to take post-compulsory physics. The impact of the programme was explored from the perspective of the teacher participants, the programme tutors and the teachers' senior managers who authorise attendance on professional development training courses. Although teachers and senior managers viewed ARP as an unmitigated success in improving classroom practice, the evaluation raises some other important implications for teaching physics and the professional development of physics teachers. Relatively few teachers have experience of action research, and there is a need for further training in this area. The study also highlights the key role of senior managers in giving physics teachers access to appropriate professional development and opportunities to carry out suitable activities in the classroom.