1. Clinical Effectiveness Unit, Royal College of Surgeons of England, London, UK
2. Leeds Institute of Medical Research, School of Medicine, University of Leeds, Leeds, UK
3. Department of Health Services Research & Policy, London School of Hygiene & Tropical Medicine, London, UK
4. Division of Neurosurgery, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
5. Department of Research, Royal College of Surgeons of England, London, UK
6. Department of Neurosurgery, Leeds Teaching Hospitals NHS Trust, Leeds, UK