This overview of how Islam is understood and practised in British and European prisons is an indispensable primer for prison and legal practitioners and policy-makers and contributes a much-needed evidence-base to a controversial subject.Based on original evidence from 279 Muslim prisoners and 79 prison officers, it explores how Muslims come to be incarcerated, how the practice of Islam affects rehabilitation, the types and effects of Islamic conversion and the professional practice of officers and chaplains. The authors also investigate the common belief that incarceration fosters Islamist extremism. Based on this evidence, they suggest improvements to provision and rehabilitative opportunities for Muslim prisoners.