In both cases the romance follows the prose rendering of Borron's Joseph of Arimathea and Merlin, and precedes a Mort Artus, thus forming part of a complete cycle.
When the founding of the Round Table is ascribed to Merlin it is generally in close connexion with the Grail legend, forming the last of a series of three, founded in honour of the Trinity - the first being the table of the Last Supper, the second that of the Grail, established by Joseph of Arimathea, The number of knights whom the table will seat varies; it might seat twelve or fifty or a hundred and fifty; nowhere, save in Layamon, do we find a practically unlimited power of accommodation.
The "sudario" from which it takes its name is asserted to be the shroud in which Joseph of Arimathea wrapped the body of Jesus.
The Glastonbury thorn, planted, according to the legend, by Joseph of Arimathea, has been the object of considerable comment.
According to the legends which grew up under the care of the monks, the first church of Glastonbury was a little wattled building erected by Joseph of Arimathea as the leader of the twelve apostles sent over to Britain from Gaul by St Philip. About a hundred years later, according to the same authorities, the two missionaries, Phaganus and Deruvianus, who came to king Lucius from Pope Eleutherius, established a fraternity of anchorites on the spot, and after three hundred years more St Patrick introduced among them a regular monastic life.
The Perceval forms the third and concluding section of a group of short romances, the two preceding being the Joseph of Arimathea and the Merlin.
In the Perlesvaus the Grail is the same, but the working out of the scheme is much more complex; a son of Joseph of Arimathea, Josephe, is introduced, and we find a spiritual knighthood similar to that used so effectively in the Parzival.
Introductory to the Galahad quest, and dealing only with the early history, is the Grand Saint Graal, a work of interminable length, based upon the Joseph of Arimathea, which has undergone numerous revisions and amplifications: its precise relation to the Lancelot, with which it has now much matter in common, is not easy to determine.
With regard to the religious form of the story, recent research has again aided us - we know now that a legend similar in all respects to the Joseph of Arimathea Grail story was widely current at least a century before our earliest Grail texts.
Legends of the part played by Joseph of Arimathea in the conversion of Britain are closely connected with Glastonbury, the monks of which foundation showed, in the 12th century, considerable literary activity, and it seems a by no means improbable hypothesis that the present form of the Grail legend may be due to a monk of Glastonbury elaborating ideas borrowed from Fecamp. This much is certain, that between the Saint-Sang of Fecamp, the Volto Santo of Lucca, and the Grail tradition, there exists a connecting link, the precise nature of which has yet to be determined.