Two entries with the named Knight of the Cart.
Knight of the Cart
Chevalier del Car
An alias given to Sir Raguidel after his body floated up to Arthur’s court in a cart on a boat.
Source
La Vengeance Raguidel | Raoul, possibly Raoul de Houdenc, early 13th century
Knight of the Cart
Chevalier de la Charette
A name given to Lancelot during his quest to rescue Guenvere from Meleagant of Gorre (Meleagaunce). In his haste to rush after the Queen, Lancelot rode his horse to death. Looking around for more transportation, he found a churl who was willing to give him a ride in a cart. Lancelot hesitated briefly and then dove in. Since riding in a cart was considered disgraceful for a knight – such a mode of transportation was reserved for criminals on their way to be hanged – shame followed Lancelot throughout the adventure.
First told in Chrétien de Troyes’s Lancelot, versions of this story contained in the Vulgate Lancelot and Malory serve to lessen Lancelot’s humiliation and to make his ride in the cart a clever, pragmatic tactic. In one passage in the Vulgate Lancelot, the title refers to Bors.
Sources
Lancelot, or Le Chevalier de la Charrete | Chrétien de Troyes, late 12th century
Lancelot do Lac | 1215-1220
Le Morte Darthur | Sir Thomas Malory, 1469-1470