Guenever is King Arthur's wife and has a relationship with Launcelot, one of his knights. She is depicted as a woman of great beauty and charm. Even though she loves Arthur and stays loyal to him politically, she continues her affair with Launcelot. She's supported by the knights of the Round Table, who see her as a symbol of feminine honor.
Even when faced with the threat of being burned for treason, Guenever doesn't give up her relationship with Launcelot until the kingdom falls. Only when some knights stop supporting her because of jealousy over Launcelot does the kingdom start to fall apart. This suggests that Guenever was the one keeping things together for a long time by balancing different interests.