1. Department of Gastroenterology, University Hospital of Wales, Cardiff, UK,
2. Department of Pathology, University Hospital of Wales, Cardiff, UK,
3. Department of Pharmaceutical Public Health, Temple of Health and Peace, Cardiff, UK,
4. Health and Behaviour Unit, Institute of Psychiatry and Maudsley Hospital, London, UK,
5. Nicotine Laboratory, Poisons Unit, New Cross Hospital, London, UK,
6. Department of Anaesthetics, Southampton General Hospital, Southampton, UK,
7. Department of Gastroenterology, Mayo Clinic, Rochester, Minnesota, USA