Charles the Great
Carlo Magno, Carolus Magnus
The Post-Vulgate Queste del Saint Graal notes that Charlemagne, emperor of the Holy Roman Empire (800-814), when he conquered England, rebuilt the Castle of Treachery (Treacherous Castle) (which had been destroyed during the Grail Quest) and created a magnificent statue of Galahad before it.
He also apparently razed Corbenic (Carbonek), the Grail Castle. His coming was foretold to Arthur by a mysterious voice.
According to La Tavola Ritonda, Charlemagne visited the castle of Leverzep, where he found statues of Tristan, Palamedes, Amoroldo, Lancelot, and Galahad. Charlemagne and his noblemen took the swords of the knights, which were hung around the statues’ necks.
Sources
Post-Vulgate Queste del Saint Graal | 1230-1240
Post-Vulgate Mort Artu | 1230-1240
La Tavola Ritonda | 1325–1350