Chronic radiation proctopathy is a frequent complication after both pelvic external radiation therapy and brachytherapy and most commonly presents as rectal bleeding. Deep rectal ulcers and fistulae are much rarer and more clinically challenging consequences. We present the case of a 72-year-old male with a history of prostate adenocarcinoma treated with brachytherapy, who was referred to our institution due to a deep painful rectal ulcer refractory to medical treatment. The ulcer presented shortly after a haemorrhoid elastic band ligation and progressed to rectourethral fistulisation despite both faecal and urinary diversion. Our case demonstrates the importance of favouring a conservative approach when dealing with an irradiated rectum.