1. Clinical Effectiveness Unit, The Royal College of Surgeons of England, London, UK
2. Department of Gastroenterology, St Mary's Hospital, London, UK
3. Department of Gastroenterology, Northern General Hospital, Sheffield, UK
4. Department of Surgery, Addenbrooke's Hospital, Cambridge, UK
5. Velindre Cancer Centre, Cardiff, UK
6. Department of Surgery and Cancer, Imperial College, London, UK
7. Health and Social Care Information Centre, Leeds, UK
8. Department of Health Services Research and Policy, London School of Hygiene & Tropical Medicine, London, UK