Activity theory (AT) is a powerful tool for investigating "artefacts in use", ie, the ways technologies interrelate with their local context. AT reveals the interfaces between e-learning at the macro- (strategy, policy, "campus-wide" solutions) and the micro-organisational levels (everyday working practice, iterative change, individual adaptation). In AT, contexts are conceived of as activity systems in which human, technological and organisational elements are interrelated and largely inseparable. Both the subjects of the activity system (internal) and the wider community (external) mediate their activities through tools, rules and roles. This paper shows how a course management system (CMS) exerts an influence over all three of these mediators, though the exact nature of this influence depends on the particular configuration of each activity system. This is illustrated with reference to two case study programmes, both of which used Moodle as their CMS, but which had activity systems structured in quite different ways; the programmes also had different relationships with their external organisational environment.