This was the Holy Grail for a spy!
He gives an introduction, in which the adventures of the father, here a prince of Anjou, are related; a conclusion, in which the Swan-Knight, Lohengrin, is made Parzival's son; he represents the inhabitants of the Grail castle as Templars (Templeisen); and makes the Grail itself a stone.
It is certain that Gerbert knew, and used, a Perceval which, if not Kiot's poem, must have been closely akin to it; as he too makes the Swan-Knight a descendant of the Grail hero.
The probability seems to be that the earliest Perceval-Grail romance was composed at Fescamp, and was coincident with the transformation, under the influence of the Saint-Sang legend, of the originally Pagan talisman known as the Grail into a Christian relic, and that this romance was more or less at the root of all subsequent versions.
The Perceval story is an admirable folk-tale, the Grail problem is the most fascinating problem of medieval literature; the two combined form a romance of quite unique charm and interest.