This comment examines the rapidly evolving ecosystem of historical research data in the United Kingdom, where cultural heritage collections are increasingly digitised, commercialised and fragmented. Historians face growing challenges in discovering, accessing and reusing data as resources move behind paywalls, and repositories remain scattered, without a national infrastructure to ensure long-term preservation or discoverability. Drawing on examples from major digital initiatives, we analyse the life cycle of historical research data and highlight the complex interplay of commercial, institutional and scholarly interests that shape access. We distinguish three types of data that emerge from historians’ typical engagements with digitised collections: derived, enhanced and aggregated data. We argue that historians must actively participate in the practices relating to the creation, maintenance and reuse of such data. This will involve new forms of citation, favouring open datasets, improving digital skills and building communities around shared resources. The comment concludes with proposals to improve discoverability, sustainability and reuse, urging the discipline to establish common standards and infrastructures to secure an equitable data commons for future research.