We aim to see if using the new enhancement techniques we can detect more polyps in patients with FAP than with standard endoscopy.The patients will undergo flexible sigmoidoscopy as usual. This will then be repeated with the auto fluorescence feature of the endoscope activated, followed by a repeat with the narrow band feature activate. Then the lining of the bowel will be sprayed with blue dye (non-absorbed) and extra dye suctioned, the viewing process will be repeated the final time. This should take approx. 5 minutes. The videos from the procedures will be anonymised and randomised for viewing by another endoscopist.