1. Clinical Effectiveness Unit, Royal College of Surgeons of England, London, UK
2. St Helens and Knowsley Teaching Hospitals NHS Trust, Prescot, UK
3. Department of Health Services Research and Policy, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK
4. Department of Epidemiology and Public Health, University College Cork, Cork, Ireland
5. James Paget University Hospitals NHS Foundation Trust, Great Yarmouth, UK
6. University of East Anglia, Norwich Research Park, Norwich, UK
7. Sheffield Teaching Hospitals NHS Foundation Trust, Royal Hallamshire Hospital, Sheffield, UK
8. Portsmouth Hospitals NHS Trust, Queen Alexandra Hospital, Portsmouth, UK