1. Clinical Effectiveness Unit, Royal College of Surgeons of England, London, UK
2. Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, UK
3. The John Goligher Colorectal Surgery Unit, Leeds Teaching Hospitals NHS Trust, London, UK
4. Department of General Surgery, Manchester Royal Infirmary, Manchester, UK
5. Faculty of Medicine and Health, University of Leeds, Leeds, UK