ROCSS aims to assess whether a biological mesh (collagen tissue matrix) reduces the incidence of clinically detectable stoma closure site hernias at two years compared to standard closure techniques. The primary outcome is Occurrence of clinically detectable hernias at two years post randomisation. Other outcomes include surgical re-intervention rate, surgical complications at 30 days post-operation and 1 year post-randomisation, quality of life and post-operative pain, cost-benefit analysis and radiological hernia rate at one year post-randomisation (an exploratory analysis will compare radiological hernia rate at 1 year with clinical hernia rate at 2 years to assess the value of using a CT scan as an early diagnostic tool of incisional hernias).