Tom Leather describes in this article the process by which he and his department extended their ancient history curriculum through an interpretations enquiry about Cyrus the Great. This tested both the subject knowledge of a number of members of the department, and their planning process. His reflections are illuminating not just as an example of how to plan an enquiry where teacher subject knowledge is initially patchy, but also of how to replan an enquiry following its first teaching – and even of the way in which the HA’s Quality Mark assessment process can help an enquiry’s development.