Edward I of England (1272-1307), best known to modern audiences as 'the Hammer of the Scots' and the founder of the English Parliament, corresponded with hundreds of aristocrats and officials. Several thousand of these letters survive. Letters were a crucial part of his political strategy. They facilitated governance by directing royal representatives scattered over a large realm, and thus enabled the king to consolidate power in the wake of the baronial rebellion that occupied the last decades of his father's rule. Adopting a case study approach, this thesis argues that the rhetoric of such administrative correspondence was politically meaningful despite its often formulaic appearance. Reading hitherto unexamined letters in light of both contextual detail and the standard epistolary structures advocated by medieval theorists I interpret these sources as social artefacts that both reflected and sought to influence the relationship of the political community to the crown. In so doing, I suggest a new understanding of how kingly authority was made and maintained in the 13th century. My approach provides a method for reading other extant royal letters as episodes of strategic communication, not simply and only as relics of a well-developed medieval bureaucracy.