“…Across the case studies, of BASE and GEMS a mixture of different classic behavioural theories were being considered and tested, such as the use of Self-Determination Theory, Theory of Planned Behaviour (individuals attitude, subjective norms, and perceived behavioural control) and Social Cognitive Theory (reciprocal determinism, behavioural capability, expectations, observational learning, reinforcements, and self-efficacy – seen as the most personal factor in changing behaviour) were used (Adamson et al, 2016; Learmonth et al, 2017; Learmonth et al, 2021). Other examples of behavioural theories can be seen in BASE with the COM-B, (capability and/or opportunity and motivation - as three key factors capable of changing behaviour) (Learmonth et al, 2021) that can help explain behaviour change in adopting exercise behaviour for those persons living with MS as they can target correlates of physical activity behaviour and consider the demands of living with MS. Further, in the BASE document source (Learmonth et al, 2021) the importance of including a realist theory approach (Brockschmidt & Wadey, 2022) to programme implementation (a theory that explains how and why particular types of interventions work to generate the outcome/s of interest) was indicated. This can help explain “how the intervention works”, “why does the intervention work”, how strategies bring about intended or unintended results, “for whom does it work” and “in what circumstances does it work” (Pawson et al, 2005).…”