We will argue that a 'model system' approach is a powerful one in ecology, in which a well characterised system can be compared with a series of less-intensively researched systems arrayed along significant environmental gradients. In this way, a series of small, 'manageable' projects devoted to the same system, lend a strength and significance to each other that is not apparent from a similar total effort expended less systematically. Broadstone Stream, a small, acidic and hitherto fishless stream in southern England, has one of the most thoroughly characterised communities of all, and has been set in the context of a series of other streams of differing pH and hydraulic properties. We will explore how theory has been tested and developed in a variety of areas including: a) density dependence, disturbance and stability, b) food web structure and links scaling, c) body size and interactions strengths, and d) geographical population structure, dispersal and links between local systems. The dominant large-bodied predatory invertebrates are richly connected in the food web and have stable populations apparently regulated by density-dependence, such that the dynamics of their populations are independent of other local systems and persistent in the face of pulse disturbances. The changes in this system over almost thirty years, in which acidity has ameliorated, have been marked and show how communities respond to press perturbations.