Much has been written about the challenges of teaching discrete mathematics and formal methods. In this paper we discuss the experiences of delivering a course that serves as an introduction to both. The one-week intensive course, Software Engineering Mathematics, is delivered as part of the University of Oxford's Software Engineering Programme to groups of professional software and security engineers studying for master's degrees on a part-time basis. We describe how a change in the course's emphasis -- involving a shift towards a focus on modelling-based group exercises -- has given rise to some pleasing results.