Queen Guinevere (/ˈɡwɪnᵻvɪər/; Welsh: Gwenhwyfar), often written as Guenevere or Gwenevere, was the wife of legendary King Arthur. She first appears as Guanhumara (with many spelling variants in the manuscript tradition) in Geoffrey of Monmouth's pseudo-historical chronicle of British history, the Historia Regum Britanniae (written circa 1136 AD) and is first found in medieval Welsh prose in the mid-late 12th century tale Culhwch and Olwen as Arthur's wife Gwenhwyfar. In medieval romances, one of the most prominent story arcs is Queen Guinevere's love affair with her husband's chief knight, Lancelot. This story first appeared in Chrétien de Troyes's Lancelot, the Knight of the Cart and became a motif in Arthurian literature, starting with the Lancelot-Grail of the early 13th century and carrying through the Post-Vulgate Cycle and Thomas Malory's Le Morte d'Arthur. Guinevere and Lancelot's betrayal of Arthur preceded his eventual defeat at the Battle of Camlann by Mordred.