Enquiry form
General enquiries:
+44 (0)207 935 4444
Book a consultation:
+44 (0)207 616 7693
Self-pay enquiry:
+44 (0)203 219 3315
The London Clinic
Professor Siwan Thomas-Gibson is a gastroenterologist and specialist endoscopist at St Mark’s National Bowel Hospital London. She is the Dean of St Mark’s Hospital Academic Institute and Professor of Practice in Gastrointestinal Endoscopy at Imperial College London.

Make an appointment

Fast track your treatment with Professor Siwan Thomas-Gibson. Call us on 020 3944 1073.

Book appointment now

Your call may be recorded for training and monitoring purposes.

Specialties and sub-specialties

Colonoscopy (diagnostic and therapeutic)
Bowel Cancer Screening (accredited 2007)
Detection and prevention of bowel cancer in normal and high risk conditions
Diagnosis and management of gastroenterology conditions
Diagnosis and management of inflammatory Bowel Disease

Professional profile

Professor Thomas-Gibson specialises in the delivery of high quality and safe colonoscopy; bowel cancer screening and the detection and endoscopic management of early colorectal neoplasia in inflammatory bowel disease and inherited cancer and polyposis syndromes. She has been an accredited bowel cancer screening colonoscopist since 2007.

She manages patients with a variety of gastrointestinal conditions including inflammatory bowel disease, irritable bowel syndrome, indigestion and those with bowel symptoms following cancer treatment.

Her research interests include the development of high quality and safe endoscopy, improving endoscopic training and assessment and developing new ways of investigating and managing bowel problems such as polyps. 

In 2018 she was awarded the prestigious British Society of Gastroenterology Hopkins prize for her achievements in endoscopic research. She was Chair of the Joint Advisory Group for Gastrointestinal Endoscopy 2017-2020 where she launched the JAG Improving Safety and Reducing Error in Endoscopy strategy. 

She is frequently faculty on national and international meetings, performing and teaching live endoscopy. She has supervised a number of PhDs and MDs and has over 100 academic publications including several National Guidelines as well as authorship in several books. She was awarded a Chair at Imperial College London in 2020 becoming a Professor of Practice in Gastrointestinal Endoscopy.

Current posts

  • Consultant gastroenterologist and specialist endoscopist, Deputy Director Bowel Cancer Screening
    St Mark’s National Bowel Hospital London
  • Dean
    St Mark’s Hospital Academic Institute
  • Professor of Practice in Gastrointestinal Endoscopy
    Imperial College

Current teaching posts

  • Honorary Senior Lecturer
    Imperial College London

Medical training

Year qualified 1992
  • St Mary's Hospital, Imperial College London 1986
  • MD, Imperial College London 2006


Early signs of visible and invisible cancers
The London Clinic
This World Cancer Day, to raise awareness of both visible and invisible cancers, two of The London Clinic’s consultants highlight some key symptoms and what they mean for patient care.
Bowel cancer, symptoms and screening
The London Clinic feature
For Bowel Cancer Awareness Month, Dr Siwan Thomas-Gibson discusses the disease and the importance of screening.

Main numbers

General enquiries: 020 7935 4444 Appointments: 020 7616 7693 Self-Pay: 020 3219 3315

Contact numbers for service departments

Other numbers

Concierge service: 020 3219 3323International office: 020 3219 3266Invoice and payment enquiries: 020 7616 7708Press office: 020 7616 7676

Your call may be recorded for training and monitoring purposes.

Close menu