1.1 The operation of PFI prisons by the private sector is governed by contracts with the Commissioner for Correctional Services (whose office forms part of the Home Office). Each contract runs for 25 years and sets out the level of service which contractors should provide, the payment system, and the mechanisms by which the Commissioner can make financial deductions for poor performance. The contracts set out detailed operational requirements, usually under seven broad headings (Figure 7). Although the operational requirements are detailed, some allow the contractor flexibility. For example, although contracts stipulate the number of staff who should be on each wing of the prison, these numbers are usually indicative and the contractor is required to provide sufficient staff to provide a safe and secure prison. This reflects the essence of the PFI approach which is based on achieving outcomes, or outputs, rather than stipulating inputs.