This case study describes consultancy work carried out as a trainee health psychologist which took place in the Clinical and Health Psychology department at an NHS Trust. The overall aim of the consultancy was to develop an evidence-based psychological intervention to improve motivation, confidence, and self-efficacy by promoting behaviour changes in post-bariatric surgery patients. Following delivery of the intervention a separate evaluation of the existing Bariatric Surgery Support Group was conducted to assess the effectiveness of the intervention and highlight any unmet needs. The ‘contact client’ for the project was one of the Senior Clinical Psychologists working in the Complex Eating, Weight and Bariatric Surgery Services within the Trust. The case study involved collaboration with various stakeholders including clinical staff, allied health professionals, and the patients themselves, and will focus on the Relationships area of the consultancy framework for health psychologists; in particular, on building trust and maintaining rapport with those key stakeholders. This includes sensitively navigating delays in client communication and acknowledging the responsibility of working with vulnerable patients and their expectations, and these areas will be reflected on throughout the chapter.