Concerns about fake news and media manipulation are commonplace in contemporary society, and, throughout the twentieth century, historians regularly presented the First World War as an era of manipulated public messages. Yet, despite broad statements about the impact of press censorship in First World War Britain, publication of an official history of the ‘D’ notice system, and growing revision of historical understanding of the interaction between the state, the press, propaganda, and the public during the war, no thorough assessment of the content of the D notices issued by the Press Bureau to newspaper editors has been undertaken. This article provides a thorough analysis of the more than seven hundred notices issued during the war years. While drawing attention to several exceptions which exceeded plausible claims of a threat to security, it argues that most notices genuinely sought to protect potentially dangerous information and that casual assumptions about misleading state press management are not borne out by a close reading of the actual notices issued.