The formerly named "Dangerous and Severe Personality Disorder" (DSPD) units are no longer standalone services within the criminal justice system in England and Wales. These sites now provide personality disorder treatment services in the high-security prison estate as part of the new national Offender Personality Disorder (OPD) Pathway Strategy. The OPD Pathway intends to take responsibility for the assessment, treatment, and management of offenders who are likely to have a personality disorder and who present a high risk of re-offending (men and women) and serious harm to others (men). Further PD treatment and progression services are being commissioned in lower security prisons and in the community as part of the new PD Strategy. While the suitability criteria for the two male high-security PD treatment sites are the same, the individual units have their own assessment and treatment methods. This article aims to communicate the referral, assessment, and treatment methods employed within the prison-based Westgate Personality Disorder Treatment Service, HMP Frankland.