1. Department of Surgery and Royal shrewsbury Hospital, Mytton Oak Road, Shrewsbury, shropshire SY3 8XQ, UK
2. Department of Anaesthesia, Royal shrewsbury Hospital, Mytton Oak Road, Shrewsbury, shropshire SY3 8XQ, UK
3. Department of Surgery, Wharfedale General Hospital, Newall Carr Road, Otley, West Yorkshire LS21 2LY, UK
4. Good Hope Hospital, Rectory Road, Sutton Coldfield, West Midlands B75 7RR, UK