Hollesley Bay began in 1887 as a Colonial College training those intending to emigrate. In 1938 the Prison Commission acquired Hollesley Bay to train young offenders in the Borstal system. In 1983 Youth Custody replaced the Borstal system and in October 1988, when the CJA 1988 came into force, Hollesley Bay became a YOI. In 1982 Warren Hill opened to accommodate Cat C young offenders in a closed environment alongside Hollesley Bay Open prison. In April 2002 though retaining some shared services, Hollesley Bay and Warren Hill became separate establishments, the Open complex retaining the name Hollesley Bay. The establishment provides different regimes for adult Category D offenders - life sentence prisoners at the end of their custodial time and young offenders.

