The Strengthening Families Programme 10-14 (SFP10-14; UK) is a seven-session DVD-based family skills training programme. While the programme has been extensively evaluated in the United States, no randomized controlled trial (RCT) of the SFP10-14 has been conducted in the United Kingdom. This exploratory Phase II study was an evaluation of a universally delivered prevention programme using a mixed-methods design study blending both quantitative and qualitative data. It aimed to examine intervention versus control differences in young person's substance use, aggressive behaviours and school absence, parenting behaviour and measures of family life. All parents/carers (n = 53) with a young person aged 10-14 years (n = 69) attending three schools in different locations in England were invited to complete self-report questionnaires pre- and post-intervention, and at 3 months after completion of the SFP10-14 (UK). A purposive sample of parents/caregivers (n = 16) and young people (n = 14) provided qualitative feedback from participating families. Participant recruitment to the study was slow and many families were reluctant to be randomly allocated, instead indicating a preference for the SFP10-14 (UK) group. Rather than abandoning the trial, a decision was made to proceed as a quasi-experimental study, that is, without randomization. (Contains 2 tables and 1 figure.)