1. The Royal Wolverhampton NHS Trust, Wolverhampton, WV10 0QP, UK
2. Medical Workforce Unit, Royal College of Physicians, London, NW1 4LE,UK
3. Research Department of Medical Education, University College London Medical School, London, WC1E 6BT, UK
4. Sandwell and West Birmingham NHS Trust, West Bromwich, B71 4HJ, UK