Lecture recordings are increasingly used to supplement lecture attendance within higher education, but their impact on student learning remains unclear. Here we describe a study to evaluate student use of lecture recordings and quantify their impact on academic performance. Questionnaire responses and online monitoring of student's access to recordings indicate that approximately 75% students use this material, the majority in a targeted manner. In contrast, a small subset of students (approximately 5%) are highly dependent on recordings downloading every lecture, and viewing the material for long periods, such that this represents a large proportion of their independent study. This "high user" group is atypical, as it contains a high proportion of dyslexic and Non-English Speaking Background students. Despite high usage, lecture recordings do not have a significant impact on academic performance, either across the cohort or with students that use the recordings. Overall, this approach appears to be beneficial, but may reduce lecture attendance and encourage surface learning approaches in a minority of students. (Contains 5 figures.)