It is difficult to say whether prison life is ‘well’ supervised by judicial and other legal authorities in England and Wales. This article explores a number of important bodies which all have a role in monitoring what goes on in prisons: HM Chief Inspector of Prisons, Independent Monitoring Boards, the Prison and Probation Ombudsman, NGOs as well as the formal courts (including coroners’ inquests). It is particularly difficult to ensure the fair treatment of prisoners within a system which gives wide and discretionary powers to those who run prisons. The challenge is all the greater at a time when prisons are increasingly privatised, and services are subject to increasing competition. Prisons are run behind substantial walls, both solid and metaphorical. The subject is under-explored in the literature – little has been written on the effectiveness of prison monitoring, especially in the academic literature, and empirical studies are even rarer. This article seeks to question what effective monitoring might look like, questioning how ‘visible’ prisons and prisoners are to the outside world. There are many eyes looking inside the prison: but what do they see, and what are they meant to do about what they see?