Participants and Recruitment

Sampling was purposive and guided by principles of information power.²⁵ Those tasked with implementing smoke-free policies nationally working within HMPPS Headquarters and regionally within Public Health England (PHE) were identified by the lead researcher (LJ), contacted, and invited to participate. At an establishment (local) level, interviews were completed with HMPPS and Healthcare staff working in 3 male prisons; selected to provide variety in relation to smoke-free policy, security level, size, prisoner occupancy, and the typical length of stay (for study prison characteristics see Supplementary File 2). Individuals who had a lead role in introducing and/or continued delivery of smoke-free policies were identified to researchers by the prison Governor/Deputy Governor and Head of Healthcare. All staff identified were approached by LJ to discuss the project and all consented to take part. Preliminary analysis (LJ and JW) concluded that our sample size of 28 held appropriate information power for recruitment to cease. Interviews were completed between August and November 2019, roughly 4 years after open estate introduced the partial smoke-free policy and 16 months after the last closed prison implemented a complete smoke-free policy.