Geoffrey of Monmouth, a celebrated chronicler and ecclesiastic of the 12th century, born in Monmouth, where he was educated in a Benedictine monastery; in 1152 he was made bishop of St. Asaph; his Latin “Chronicon sive Historia Britonum” contains a circumstantial account of British history compiled from Gildas, Nennius, and other early chroniclers, interwoven with current legends and pieced together with additions from his own fertile imagination, the whole professing to be a translation of a chronicle found in Brittany; this remarkable history is the source of the stories of King Lear, Cymbeline, Merlin, and of Arthur and his knights as they have since taken shape in English literature; d. about 1154.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Gentz, Friedrich von * Geoffrey Saint-Hilaire, Étienne