Protecting prisoners’ rights requires a multi-layered approach, and any mechanisms for doing so need to be effective within the political and legal cultures of each jurisdiction. The Chief Inspector of Prisons has the statutory duty to inspect prisons in England and Wales and to report on them to the Home Secretary, in particular on the treatment of prisoners and conditions in prisons. Inspection is a key part of the public accountability for prisons. Prisons operate out of sight of the general public. Published reports alert Parliament and the public to what is actually happening in their prisons. The United Kingdom system of prison inspections is an important part of the protection of prisoners’ rights. The relatively new Protocol to the UN Convention against Torture and Inhuman and Degrading Treatment requires states parties to have in place a “national preventive mechanism” for regularly visiting and monitoring all places of detention. Prisons Inspectorates are a key part of that mechanism within the United Kingdom. This article focuses on the Prisons Inspectorate and discusses its methodology and criteria for inspections, based on international human rights standards, the effectiveness of the Inspectorate, its independence and relationships with other monitoring bodies, the government and the prison service, the application of the methodology to other countries outside the United Kingdom, and future developments and threats.