Dr Fell is lead paediatric gastroenterologist at Chelsea and Westminster Hospital, and Honorary Senior Lecturer at Imperial College. He runs the regional paediatric IBD for NW London, with a transition clinic to adult service within Chelsea and Westminster. He is a previous CICRA research fellow having undertaken research in mucosal inflammation and its modultaion by nutritional therapy in paediatric Crohn's disease.

He has published widely in the field of paediatric gatstoenterology, and co-authored the British Society of Paediatric Gastroenterology Hepatology and Nutrition guideline for the management of paediatric IBD. Other areas of special interest include infantile GI disorders and the intestinal consequences of food allergy.