In recent decades, public bodies in the UK have increasingly relied on models, of differing levels of sophistication, to assist them with decision-making. However, officials are often reluctant to disclose such models. An important question of public law that results is if and when a public authority is under a duty to disclose a model. This article argues that there has now emerged a clear line of authorities which establishes a strong common law presumption in favor of disclosure. The principles around this presumption are likely to be an increasingly contested aspect of administrative law in the coming years and a clear legal framework is required. We therefore propose a three-stage approach which is both faithful to precedent and sensitive to the tensions surrounding this issue.