The paper explores the value of practitioner enquiry in the development of common language and shared understandings for a group of mid-career professionals from a variety of public service backgrounds, brought together to formulate responses to the English agenda for integrating services. It draws upon data gathered from multi-professional action learning and focus groups via a collaboration between an English University and six regional authorities. Theories of "third space" and "hybridity" are engaged in arguing that the achievement of "integrated" or "trans-professional" knowledge can develop within "undecided" reflective spaces through which new ways of working are discovered. It concludes that collaborative multi-professional practitioner enquiry offers a realistic means of embedding this challenging aspect of policy. (Contains 4 notes.)