This is the second of two articles on Developing Students' Learning through Mathematical Writing (a Maths, Stats & OR Network (MSOR Network) funded mini-project) at Queen Mary, University of London (QMUL). These articles report on the Mathematical Writing (MW) course at QMUL, devised by Professor Franco Vivaldi. The investigation into student learning on the MW course was carried out by staff in the Thinking Writing (TW) initiative at QMUL which works to develop the teaching and assessment of writing (see http://www. thinkingwriting.qmul.ac.uk/). In this article, we begin by describing the MW course (see MW course page-http:// www.maths.qmul.ac.uk/~fv/teaching/mw/). We then discuss the aim of our study and research methodology. The rest of the article focuses on a case study of one student's learning on the course. We explore this case in detail in order to explicate our interpretation of the data.