It seems uncontentious that policy development should be informed by evidence, and that researchers should be engaged to assess available evidence. In this paper, we tell the story of a Rapid Evidence Assessment (REA) about school exclusion, a task intended to inform a 'root and branch' policy review. Drawing on Carol Bacchi's 'What's the problem?' approach, we use the project brief and the changing texts that we wrote to show that, while we began reviewing literature with a generous definition of exclusion, our focus progressively narrowed to encompass only the literatures that fitted with the pre-existing policy definition. Our story shows that a need to focus on big E Exclusion policy eliminated insights about little e exclusion, in particular how wider social relations and the school itself were implicated. The case raises critical questions about how policy evidence about exclusion is produced -- and limited.