AlthoughThe History of the Holy Grail
opens the Vulgate Cycle, it was added after the events described in Lancelot
and The Quest of the Holy Grail
were already an established part of the Arthurian story. It is, in Hollywood terms, a `prequel', and relates the story of the Grail from its first appearance at the Crucifixion up to the point where it is placed by Alain, the Fisher King, in the castle of Corbenic, whose inhabitants then await the arrival of the chosen Grail knight. Many points in the narrative are designed to foreshadow or to explain the later adventures connected with the Grail, but it also draws on the stories in the apocryphal gospels and other legends of the crucifixion such as the story of Veronica, as well as unrelated material such as the story of Hippocrates. But it also provides many details about the Grail itself which are not found anywhere else. It is less chivalric in tone from the subsequent books of the Vulgate Cycle, and relatively few copies of the original survive.
For a full description of the Vulgate Cycle see the blurb for the complete set.