Designing new educational experiences, which utilize novel technologies, are usable by teachers and learners and integrate well into existing, everyday educational contexts is extremely difficult. In this paper we describe the process of Human Centred Design as a cyclic process of evolution. An initial system design vision is communicated to a range of stakeholders and revised as informed by feedback from these users to produce a modified vision. A cycle of presentations of the vision and modifications lead to the creation of system prototypes that are increasingly grounded in a genuine understanding of user needs and context. The latter stages of this process employ contextually evaluated semi-functional and functional prototypes, associated documentation and an iteratively refined framework for data capture and analysis. We use the HOMEWORK system development as a case study to demonstrate the use of this approach and to illustrate the benefits that user involvement in the design process can bring to bear upon the development of an Interactive Learning Environment. We describe the type of methodology that can help designers to reap these benefits and the resource implications arising from this work. We conclude that the key output from the design process at each phase is more than the latest version of the system prototype and a modified system vision; it is also the analytical methodology that has been iteratively developed in parallel to the system software. It is this meta level analytical map that can add rigor to the design process and help to make the findings generalise beyond the particular users involved in the design process.