The paper explores the implications of being a social worker seconded to a Mental Health Trust based on narrative interviews with mental health social workers. As part of a wider study, thirteen mental health social workers from across England were interviewed individually about their experiences of being seconded to a Mental Health Trust. Building on the work of Andrew Pithouse, the findings reveal the (in)visibility of mental health social work. The social workers were isolated within Health Trusts with minimal links to their Local Authority employers. They struggled to articulate and define social work. Instead, social work was depicted as being indefinable, involving working in liminal spaces and as filling the gaps left by other professions. Furthermore, the social workers were unable to make social work visible as social work is not ‘seen’ by the other members of the team. Finally, the social workers were unable to make social visible through supervision if they did not have a social work manager. The paper ends with an unexpected outcome of the research: the notion of the research interview as surrogate supervision.