This chapter charts the author’s own learning pathway as a senior forensic psychologist working with those convicted of terrorist offences in the UK, from the Maze prison in Northern Ireland as a senior member of HM Inspectorate of Prisons during the period of the Good Friday Peace Agreement in 1998, through to casework in England & Wales with those convicted of terrorist offences between 2008 and 2011. These experiences created an ongoing research interest into the etiology of terrorist offending from a psychological perspective. Empirical work with convicted terrorist offenders over three years within a small team of psychologists informed a methodology for the assessment and management of the risk of terrorist re-offending for the British correctional system in 2012, and interventions to assist in their disengagement and/or desistance. This learning in turn informed the Prevent strand of the UK government’s counter-terrorism strategy for countering violent extremism in the community.2 More recently, as an academic this work has developed into a theorized typology of terrorists as more evidence has come to light about the contributions of criminality and individual psychopathology to terrorist violence. This chapter seeks to map this journey from empirical beginnings to emerging theory.