Borstal institutions Offenders aged 15 and under 21, convicted of an offence punishable with imprisonment, were sent from six months to two years to a (UK) Borstal institution (Patterned originally on a reformatory opened at Borstal, Rochester, under the Prevention of Crime Act 1908) where detention was accompanied by training and instruction. Sentences of this nature were abolished by the C.J.A. 1982 (UK), s. 1(3).