We hypothesise that the known interaction of chemotherapy and radiotherapy are increased by the addition of further cancer therapies, specifically drugs that block immune system cells, like durvalumab. These drugs may supplement the effect of radiotherapy and chemotherapy in muscle invasive bladder cancer and thus improve local control and the spread of the disease. The aim of RadIO is therefore to assess the safety, feasibility and efficacy of a combination of radiotherapy with durvalumab and chemotherapy in muscle invasive bladder cancer using a randomised multi-arm multi-stage design.