1 Department of Surgery and Cancer, Imperial College London, London, United Kingdom. Electronic address: g.hanna@imperial.ac.uk.
2 Department of Surgery and Cancer, Imperial College London, London, United Kingdom.
3 Department of Surgery and Cancer, Imperial College London, London, United Kingdom; J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Prague, Czech Republic.
4 Department of Gastroenterology, Charing Cross Hospital, London, United Kingdom.
5 Department of Gastroenterology, Homerton University Hospital, London, United Kingdom.
6 Department of Gastroenterology, St George's Hospital, London, United Kingdom.
7 Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Gastroenterology, West Middlesex University Hospital, London, United Kingdom.
8 Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Surgery, Chelsea and Westminster Hospital, London, United Kingdom.
9 Department of Surgery and Cancer, Imperial College London, London, United Kingdom; Department of Gastroenterology, St Mark's Hospital and Academic Institute, London, United Kingdom.