1. Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine , London , UK
2. Department for Targeted Intervention, Division of Surgery and Interventional Science, University College London, NHS foundation Trust , London , UK
3. Clinical Effectiveness Unit, Royal College of Surgeons of England , London , UK
4. Trent Oesophago-Gastric Unit, City Campus, Nottingham University Hospitals NHS Trust , Nottingham , UK
5. Department of Colorectal Surgery, Royal Alexandra Hospital , Paisley , UK
6. College of Medicine and Health, University of Exeter , Exeter , UK
7. Bristol Surgical Trials Centre, University of Bristol , Bristol , UK