The Prevent policy was introduced in 2003 as part of the UK counter-terrorism strategy (CONTEST) with the aim of preventing the radicalisation of people to terrorism. In 2015, it was given a statutory footing in the Counter-Terrorism and Security Act and it became a legal duty for Higher Education Institutions among others. Since then, Higher Education Institutions have been working to ensure their compliance with the legal duty. This article reflects on the implementation of the Prevent duty in one university. It is informed by an engagement with the Prevent group in the university which was created to implement the Prevent duty. The article argues that academic expertise had little impact in shaping the implementation of the Prevent duty at the university because the epistemic stance of counter-terrorism side lines expertise and evidence so that it can maintain its coherence and integrity. Specifically, the impact of academic expertise was limited because critically oriented academic expertise complicates a straightforward implementation of the legal duty, a state-centric orientation in the Prevent group constrained the horizon of discussion, and a crisis of knowledge at the heart of counter-terrorism replaces expertise and evidence with ideology.