The purpose of this discussion paper is to describe the transition over the past five years of a highly specialist group treatment programme to a tiered public health delivery model within the offender personality disorder (OPD) pathway. The focus of this journey of transformation has been the Challenge programme, currently the only OPD specialist service for men with sexual convictions in the community in England and Wales, and now a pan-London service. To read the full article, choose Open Athens “Institutional Login” and search for “Midlands Partnership”.