Lancelot slaying the protectors of false Guinevere 1300-25. Manuscript 805. In the Arthurian legend, Sir Lancelot is one of the Knights of the Round Table. In most of the French prose romances and works dependent on them he is characterized as the greatest and most trusted of Arthur's knights, and plays a part in many of Arthur's victories. Arthur's eventual downfall however, is also brought about in part by Lancelot, whose affair with Arthur's wife Guinevere destroys the unity of Arthur's court.