This is a multicentre, open-label, Phase I/II study of enadenotucirev in patients with either solid tumour of epithelial origin not responding to standard therapy or for whom no standard treatment exists (Phase I dose escalation stage Single cycle), mCRC not responding to standard therapy (Phase I dose escalation Repeat cycle cohort expansion stage ), mCRC not responding to standard therapy or advanced or metastatic bladder cancer not candidate for chemotherapy (Phase Ib) or mCRC in stable disease or partial response after 3-4 months of first line standard of care chemotherapy (Phase II).