1. Department of Surgery, Portsmouth Hospitals University NHS Trust , Portsmouth , UK
2. School of Pharmacy and Biomedical Sciences, University of Portsmouth , Portsmouth , UK
3. Clinical Effectiveness Unit, Royal College of Surgeons of England , London , UK
4. Department of Health Services Research and Policy, London School of Hygiene & Tropical Medicine , London , UK
5. Department of Clinical Oncology, Velindre Cancer Centre, Velindre University NHS Trust , Cardiff , UK
6. Department of Gastroenterology, Sandwell and West Birmingham Hospitals NHS Trust , Birmingham , UK
7. Department of Surgery, Oxford University Hospitals NHS Trust , Oxford , UK
8. Department of Surgery, Guy’s and St Thomas’ Hospital NHS Foundation Trust , London , UK