This case study explores the challenges that Master's students encounter when learning to write in academic English as part of a UK postgraduate course, after having achieved the required IELTS entry score. Interviews with six Chinese and Japanese learners at different stages of the Master's study revealed more sophisticated writing difficulties than they had previously experienced. Although students were largely managing their written work overall, there were recurring challenges with critical thinking, the transition to full academic compositions, using reading to inform academic writing, presenting evidence and conveying a clear written message over demonstrating lexical or grammatical range as required in IELTS writing. Furthermore, candidates on non-standard courses (e.g. film or finance) found their assignments to be quite unfamiliar; the use of one academic test for all disciplines may be disadvantageous to some. In summary, although IELTS had provided an important first step to help students develop basic writing skills, meeting university assessment expectations necessitated considerable further progress. The required support to achieve this may be somewhat underdeveloped in the existing model of international postgraduate study, for the participants in this paper. This research follows as part of a larger project, which focussed on IELTS test preparation in China and Japan (Clark 2018).