Concern is increasingly being expressed about the lack of provision for mentally disordered offenders, who by default end up within the penal system. Gunn et al (1991) in a study of sentenced prisoners identified a significant number who were mentally disordered to be in need of psychiatric treatment. Among these, 0.4% were considered to be mentally handicapped. Recent reports have emphasised the importance of diverting these individuals from the criminal justice system (Woolf & Tumin, 1991; Home Office, 1990; British Medical Association, 1990). However, the majority of such offenders do not fulfil the criteria for admission to hospital under the Mental Health Act 1983. Most are not overtly mentally ill and do not require treatment in conditions of medium security such as exist in regional secure units. However, it is not clear what provision there should be for such individuals. Smith (1988) described an open forensic unit for mildly mentally handicapped offenders (the Leander Unit). She concluded that there was a need for a specialised service to cater for these patients, who were neither appropriately nor adequately provided for by the general psychiatric services, the mentally handicapped services, regional secure units or special hospitals. Unfortunately, in practice there are very few facilities for this group of patients.