Bertelot was the brother of the despised Breuse Sans Pitie, whom Bertelot often accompanied on his marauding. He was defeated once by Lancelot.
Sir Bliant, defending Lancelot from the brothers while Lancelot was mad, struck off Bertelot’s hand.
It is possible, but unlikely, that Bertelot could be identified with Sir Bertholai of the Vulgate.
Source
Le Morte Darthur | Sir Thomas Malory, 1469-1470