Reimagining the Past in the Borderlands of Medieval England and Wales challenges the standard narrative of the relationship between England and Wales in the Middle Ages, which assumes that after Edward I's conquest of Wales in 1282, England grew increasingly powerful while Wales faded into insignificance. This book shows instead that concepts of Welsh and British history (as told by Geoffrey of Monmouth and others) were in fact enduringly potent instruments of political power in late medieval Britain, and came to have a profound effect on late medieval thought about empire, monarchy, and succession. The introduction of these ideas into the broader stream of political consciousness was brought about by the interests of baronial families in the March of Wales (the borderlands between England and Wales). Georgia Henley demonstrates the emergence of a particular brand of marcher literature interested in succession, land rights, and the narrative scope of Geoffrey of Monmouth. Marcher patrons leveraged their ancestral, political, and ideological ties to Wales in order to strengthen their political power, both regionally and nationally, through the patronage of historical and genealogical texts that reimagined the Welsh historical past on their terms. In doing so, they brought ideas of Welsh history to a wider audience and a higher degree of influence than previously appreciated.