1 Department of Colorectal Surgery, Imperial College and the Royal Marsden Hospital, Royal Marsden NHS Foundation Trust, Fulham Road, SW3 6JJ, London, UK.
2 Department of Colorectal Surgery, Imperial College and the Royal Marsden Hospital, Royal Marsden NHS Foundation Trust, Fulham Road, SW3 6JJ, London, UK. p.tekkis@imperial.ac.uk.