This paper firstly presents Statement Archaeology, an innovative and rigorous method devised to systematically operationalise the approach to historical exploration used by Michel Foucault in pursuit of the question "how do certain practices become possible at particular moments in history?" Drawing on an analysis of the theoretical basis of Foucault's broad -- and arguably equivocal -- approach, a series of methodological procedures by which it can be systematically operationalised are set out. These focus on the interrogation of "statements", through a series of questions, against three criteria: Formation, Transformation, and Correlation. Secondly, through the use of a specific policy development in English Religious Education as an exemplar, the paper establishes the potential of the approach. Deploying Statement Archaeology in relation to this example reveals that the change under investigation became possible at a nexus of changes in the rules of what is thinkable and unthinkable within different domains of discourse, and complex and messy processes of changing legitimacies and normalisations, with previously unacknowledged policy-influencers playing an important role. Many existing accounts of this change have overlooked these matters. The paper concludes by arguing that Statement Archaeology has potential significance in any domain of enquiry that seeks answers to the question "how did this particular practice become possible at that particular moment?"