This paper reviews the history of educational research, primarily in Britain, showing how the concept of research in education -- what it is, how it was done, and what its function should be -- has changed over the past hundred years. A central theme is the growing acceptance of research in education, which paradoxically, it is suggested, may have had the effect of restricting its scope. Experimental research in education originated in the late 19th century in Germany, and initially was seen primarily as psychological inquiry into learning, an academic activity whose contribution to school practice and policy issues was essentially theoretical and long term. The application of research came to be recognised in the first half of the 20th century, but it was seen as the work of experts and specialists, to be used where appropriate by teachers and administrators. The 1950s and 60s saw educational research accepted as a discipline in its own right, and brought it into closer partnership with policy and practice, with increased funding giving those who commission research greater say in design, management and dissemination. The teacher-researcher movement, initially aimed to support teachers in carrying out research themselves, developed into a more fundamental view of research as a key element in a professional approach. In summary, the role of researcher has moved from academic theorist in phase 1, through expert consultant in phase 2, to reflective practitioner in phase 3. The paper concludes with a review of recent trends, postmodernist and poststructuralist, which challenge the positivist assumptions underlying the scientific-experimental paradigm which has been dominant throughout the 20th century.