1. Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Hills Road, Cambridge CB2 0QQ, UK.
2. North West Deanery, 3 Piccadilly Place, Manchester M1 3BN, UK.
3. Sunderland Royal Hospital, Kayll Road, Sunderland, Tyne & Wear SR4 7TP, UK.
4. Centre for Applied Medical Statistics, University of Cambridge, Department of Public Health & Primary Care, Institute of Public Health, Forvie Site, Robinson Way, Cambridge CB2 0SR, UK.
5. Trafford General Hospital, Moorside Road, Davyhulme, Manchester M41 5SL, UK.