Sion is a hospital pharmacist researcher and his methodological expertise is the application of behavioural science to develop and evaluate medicines optimisation interventions. Within his PhD, he developed a 'practitioner behaviour change intervention for deprescribing in the hospital setting'. His deprescribing intervention is being tested in an NIHR Programme Grant for Applied Research across 24 hospitals and 42,000 patients in England. After completing a series of postdoctoral positions and lectureships at the University of East Anglia and University of Leicester, he returned to the University of East Anglia in 2025 as an Associate Professor of Behavioural and Implementation Sciences.

Sion plays significant local, regional and national roles in research capacity building. He is the co-lead for the NIHR Applied Research Collaboration East of England Research Capacity Development workstream, and a board member of the NIHR Incubator for Pharmacy Professionals, and leads its early career researcher capacity building.