Students' approaches to learning are heavily researched in higher education and are of particular concern in the field of mathematics where many students have been found to struggle with the transition to university mathematics. This article outlines a mixed methods study which sought to describe undergraduate mathematicians' approaches to learning using the deep-surface-strategic 'trichotomy' using the Approaches and Study Skills Inventory for Students with 414 mathematics students and semi-structured interviews with a subset of 13 at a leading British university. Analysis found that neither the 'approaches to learning' framework nor the inventory can effectively describe students' study practices and conceal important elements of how students learn advanced mathematics for examinations. Therefore, it is important that educators do not try to oversimplify students' methods using quantitative questionnaires but do seek to support those who would otherwise rely solely on memorisation as a means of passing high-stakes examinations.