This article makes a distinct contribution to the understanding of establishing multi-agency working. Using Horwath and Morrison's framework, a collaboration is described in detail, bringing multiple agencies to work with children attending a new special school for those with social, emotional and mental health (SEMH) needs, and with their families. 'Imaginal pictures' of the multi-agency collaboration are outlined, with explanations of conscious and unconscious barriers to integrated working. Lessons are identified for future multi-agency collaborations, in terms of design and vision, membership, resourcing and leadership.