An oft-repeated theme in all of Arthurian literature is the hero going on an adventure. Just as commonly he finds a wife along the way and becomes king of a foreign land. This motif can be found with Erec/Gereint, Owain/Ywain/Ivein, Peredur/Perceval in every version, but also with Culhwch, Lancelot, Gawain, and a number of lesser characters in the Arthurian world.
This hardly sounds like a kingship ritual. However, it should be kept in mind that the Celtic people had a very different approach to kingship than many later cultures. For the Celts, kingship was not the rule of the people per se, but more ownership of the land. The land was represented by a woman. The title of king was earned through a series of ritual tests symbolically proctored by the land, while inauguration itself involved a rock throne that was his final test of worthiness, a cup that would become a symbol of authority, and a maiden that symbolized the land he was to rule. The ceremony involved the new king sitting on the stone, it screaming to all the land its approval, taking the cup of kingship from the woman, and then marrying her.
With that in mind, the elements of kingship emerge in the various Arthurian stories. Owain challenges for the kingship by throwing water on a particular stone, and the resulting sound is compared to a thunderstorm. The battle that results is one that has taken many knights’ lives. Perceval sits at the Siege Perilous at the Round Table, a chair that has swallowed up many men. Both men’s survival of the test ensures that they will be the new kings of their respective realms.
The cup of kingship appears twice in the grail story. The first time is when a knight walks into Arthur’s court and takes it, spilling wine on Ginover/Guinevere in the process. The authors of the scene have made much of Guinevere’s humiliation, but the truth is that Perceval returning the cup seems to restore honor to the court, not an apology or a new dress.
It is interfesting that Guinevere appears here. Certainly it makes no sense to steal the queen’s cup if the king’s is so near. From our viewpoint on kingship, such an act would be much more insulting. However, as the symbol of the land and the cup maiden she could be the only possible target for someone hoping to usurp the throne.
The second time the cup appears there is a question that is supposed to accompany it – “For whom is the cup?” A woman is holding it, and failure to ask that one question bars him from the kingship. When he finally returnns to the Grail Castle and does ask the proper question, he is made king immediately.
The cup maiden figures prominently in all of Celtic literature, but is especially visible in Arthurian lore. There, they call for heroes, guide them to danger, occasionally help them, and eventually marry them, they are what the Irish called Medb – “she who intoxicates”. I have always found it amusing that the staple motif of Arthurian adventures is the story of a knight leaving Arthur’s court to become a king in his own right.