The Scot Thomas Dempster (ca.1574–1625) was an idiosyncratic classical scholar whose brief appointment as royal historian to James I has previously been overlooked. This article examines what Dempster wrote to explain why James chose to support him in 1615, and argues that by appointing Dempster, James reacted to recent debates about the political importance of historical research in England connected to the Society of Antiquaries, to William Camden’s publication of his history of the reign of Queen Elizabeth, and to Fulke Greville’s proposal to endow a chair of history at Cambridge University. James chose as his historian a man whose major work was a revised encyclopedia of the classical world and who practiced a more disinterested antiquarian scholarship than his English contemporaries. Dempster did not last long in his post, but James’s patronage of him is an important reminder of the acute sensitivity of historical writing in this period.