The Lancelot-Grail Cycle as we know it was not fully planned from the start. It is generally acknowledged that the Estoire del Saint Graal and the Estoire de Merlin were later additions to the Cycle, carefully presented to prepare the way for later events. However, the development of the romance from the account of the childhood of Lancelot, beginning ‘En la marche de Gaule et de la Petite Bretaigne’ (LK 1) [In the borderland between Gaul and Brittany], to the death of Arthur has given rise to greater controversy. In contrast with some early scholars such as Brugger and Bruce who ascribed a major role to vanished cycles or interpolators, Ferdinand Lot stressed the careful links made between the various branches and argued that a single author wrote the Cycle, apart from the Merlin, Jean Frappier maintained that an ‘architect’ had planned the Cycle from the account of Lancelot's childhood to the death of Arthur. Micha too argues for the unity of the Cycle.

One of the remarkable features of the Cycle is indeed its complex interlacing structure, achieved by creating links between its various branches; but there are problems in relation to the theory of an uninterrupted development of the story of Lancelot, with a son Galahad designed from the beginning to be the chief Grail hero. This can be clearly shown through a study of the manuscript tradition in relation to a passage to be found early in the account of Lancelot's childhood and which lists the three most beautiful women. The first was Guinevere, and the second Helene san Per, who figures in an adventure of Hector before Lancelot becomes a knight of the Round Table. In MS Paris, Bibliothèque Nationale de France, fr. 768, the third is described as follows: