Last updated: 16 January 2026
Category A Prison
The highest security prisons in the UK, housing those whose escape would be highly dangerous to the public, police, or national security.
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Category A Prison
Category B Prison
High-security prisons for those who do not require maximum security but for whom escape must be made very difficult.
Category C Prison
Training prisons for those who cannot be trusted in open conditions but who are unlikely to try to escape.
Category D Prison
Open prisons with minimal security for those trusted not to escape. Often used for those nearing the end of sentences.