The feasibility and efficacy of the therapy will be investigated in a randomised controlled design (n = 35) with a between-groups longitudinal design to compare key outcomes between people who do and do not receive the intervention and to estimate key trial parameters. Participants will be randomised to either an immediate intervention or a delayed intervention condition (in which they are offered the intervention after completing all assessments) using a 2:1 ratio. Participants will be randomised after completing baseline measures using an independent web-based randomisation service. The researchers will be delivering the intervention and therefore will not be blind to group allocation. Participants will be recruited from community mental health teams and standalone psychology services in the South London and Maudsley NHS Foundation Trust.