This open access book describes everyday life in Close Supervision Centres - special units within the England & Wales prison system that hold men considered too difficult or dangerous to be accommodated in mainstream prisons. Based on unprecedented access to these sites of 'deep confinement', and involving interviews with 40 men held within them, it documents in close and vivid detail the subjective experience of acutely controlled conditions, staff-prisoner dynamics, psychological power, and often tense relations between prisoners themselves. The analysis characterises the 'CSC system' as a kind of crucible: a highly intense social and relational environment, which places extreme men alongside each other in an environment of extreme restriction. In capturing the social and emotional texture of deep incarceration, including feelings ranging from hopelessness and distress to sanctuary and mental liberation, the book explores penal legitimacy, and what humans can endure, at the outer edges of state power.