Coenred's sparsely documented reign is mentioned in the "Life of Guthlac". The author, Felix, reports conflicts with the Britons: "in the days of Coenred King of the Mercians, [...] the Britons the implacable enemies of the Saxon race, were troubling the English with their attacks, their pillaging, and their devastations of the people [...]" To counter such attacks, Æthelbald, who came to the throne in 716, was once thought to have built Wat's Dyke, an earthwork barrier in northern Wales; but this now seems unlikely, since an excavation of the Dyke in 1997 found charcoal from a hearth which was radiocarbon-dated to some time between 411 and 561.