ERP 53 Guidance for Deployment and Command of Armed Officers in Home Office Prisons
This ERP relates to the police response and principles to a request from the Governor of one or more HM Prisons, for assistance in dealing with a serious internal disorder or hostage situation.
The trigger to implement this plan will come from those in command of an incident within a prison establishment who have reason to suppose that a threat or potential threat to life exists, and that mitigation of that threat is beyond the capability of the prison service.