This study explores undergraduate students' use of ChatGPT when writing essays. Three students were tasked with writing two essays each for a coursework component for a Cambridge qualification facilitated by access to ChatGPT. After writing the essays, they participated in semi-structured interviews about their experiences of using the technology. Researchers compared the transcript of the chatlog between the students and ChatGPT with the submitted essays. Analysis showed that the students relied on ChatGPT outputs to different extents, although they followed a similar process of engagement. The students shared their misgivings and points of appreciation for the technology.