This article examines the posthumous interpretation of Charles Rennie Mackintosh as a pioneer of the Modern movement using the 1933 Mackintosh memorial exhibition as a case study. The exhibition, held at the McLellan Galleries, Glasgow, was a major event in the re-popularisation of Mackintosh following his death in 1928. Using archival material only recently made available, the article focuses on the actions of the architectural critic Philip Morton Shand, Britain's highly influential ambassador for the Modern movement in the interwar period. Shand identified Mackintosh as the sole link in a linear history of the movement leading back to its putative origins in Britain. Attempting to intervene in the exhibition, Shand clashed with its organiser, William Davidson — a close friend and patron of Mackintosh. The correspondence between Shand and Davidson reveals new aspects of the Mackintosh historiography in the development of the British Modern movement.