The study was planned and conducted as an exploratory trial, without sample size calculation or a predefined primary endpoint. After consenting to taking part in the research, prisoners were randomly assigned to the yoga or control group using a Microsoft Excel randomization routine. On the first meeting, one week before the start of the 10-week intervention (henceforth, Time 1), participants were assessed with a battery of scales. This baseline assessment was conducted by two researchers and lasted, on average, 45 min. As rates of illiteracy in UK prison populations can be high (Social Exclusion Unit, 2002, The Prison Reform Trust, 2008), all instructions and questionnaire items were read to participants by one of the researchers. Rating scales, in a large coloured format, were placed in front of participants to aid responses to the questionnaires. Post-intervention assessments took place one week after completion of the 10-week course (henceforth, Time 2), at which point participants were assessed using the same measures, in addition to a cognitive-behavioural task.