From Mental Health Law Online
A prisoner can be transferred to hospital under s47. Under s47(3) he will be treated as if subject to a hospital order: s47 on its own is often called a "notional s37".
It is usually given alongside a restriction direction under s49. One exception is where the prisoner is near the end of his imprisonment, as the restrictions would soon cease and the patient would become a notional s37 patient at that stage anyway.
See Discharge of transferred prisoners.
PSO 4700: Indeterminate Sentence Manual - See chapter 15 entitled "Mentally disordered indeterminate sentence prisoners" (new version inserted by PSI 29/2010 with effect from 19/4/10)
Dept of Health, 'Good Practice Procedure Guide: The transfer and remission of adult prisoners under s47 and s48 of the Mental Health Act' (1/4/11)
Dept of Health, 'Procedure for the Transfer from Custody of Children and Young People to and from Hospital under the Mental Health Act 1983 in England' (dated June 2011, published 1/8/11)