He began to ride toward a mountain as fast as his horse could carry him. He was riding a good horse, and so was Lancelot, so that they galloped a full two leagues. Then the duke's horse grew tired, so that he fell dead beneath him from exhaustion. When Lancelot, who was riding close behind him, saw the duke on the ground, he went to him just as he was on the horse and gave him such a sword stroke on the helmet that he split him to the teeth.

Post Vulgate Cycle