1. Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, EC1M 6BQ, UK
2. Homerton Anal Neoplasia Service, Homerton University Hospital NHS Foundation Trust, London E9 6SR, UK
3. National Bowel Research Centre, Blizard Institute, Queen Mary University of London, London E1 2AT, UK
4. Barts Anal Neoplasia Centre, Department of Colorectal Surgery, Surgery and Cancer CAG, The Royal London Hospital, Barts Health NHS Trust, Whitechapel, London E1 1BB, UK
5. Cellular Pathology, Barts Health NHS Trust, London E1 2ES, UK