Leodegan’s enemies conspired to replace the true Guinevere with the false Guinevere on Arthur’s wedding night, but Merlin learned of the plan and commissioned Sir Ulfin and Sir Bretel (Brithael) to stop it. Years later, Guinevere the False formed an alliance with Bertelay (Bertholai), an old knight who had been expelled from Leodegan’s court for murder. They sent a message to Arthur proclaiming that Guinevere the False was the true queen, and that Arthur had been living with an impostor since his wedding night.
Arthur decreed a judicial trial between Gawain and Bertelay, but before it could take place, the False Guinevere captured and imprisoned Arthur. Arthur succumbed to a love potion, returned to court, and proclaimed Guinevere the False queen. Lancelot championed the real queen against three of Bertelay’s knights to prove her innocence.
In the non-cyclical Lancelot do Lac, Bertelay and the False Guinevere then admit their guilt and are burned. According to the Vulgate Lancelot, Lancelot and the true Guinevere fled Arthur’s court for Sorelois, where they lived for several years before Guinevere the False perished of an illness, confessing on her death bed.
Lancelot do Lac | 1215-1220
Vulgate Lancelot | 1215-1230
Vulgate Merlin | 1220-1235