In this article I will discuss the route by which I came to work with Cultural Historical Activity Theory (CHAT). The brief tracing of my own biography will highlight theoretical and methodological milestones. I will then discuss my current work, with colleagues, on approaches to investigating and improving the learning of professionals who are involved in interagency work, which intends to reduce the risks of social exclusion for marginal groups. In this case I will consider those young people who become excluded from school and whose needs are complex and rapidly fluctuating. This project is concerned with the learning of professionals in the creation of new forms of practice, which require joined-up solutions to meet complex and diverse client needs. We study professional learning in services that aim to promote social inclusion through supporting clients as effective actors in their worlds. At any given time in their lives individuals may take part in particular configurations of several, diverse social practices. In this discussion I will draw on recent developments in CHAT and theories of learning at work.