In his search for the Grail, Tennyson's Lancelot follows a "sweet voice singing in the topmost tower":
... as in a dream I seemed to climb For ever: at the last I reached a door ... It gave, and throe' a stormy glare, a heat As from a seventimes-heated furnace ... And yet methought I saw the Holy Grail All palled in crimson samite ... (Idylls of the King, 2:829-44).
Just over a century later, publishers regularly advertise Lancelot's vision of the Holy Grail with promises of new discoveries about the world of ancient Druids, Templars and assorted mystics. Books purporting to reveal the secret behind the Holy Grail literature of the Middle Ages are a widespread phenomenon of modern popular culture. Indeed so prevalent are they that any attempt at a comprehensive survey would be out of date as soon as it was printed. Nor, given the autodidactic nature of this writing, is there much point in trying to refute any of the assertions by unravelling the tortuous arguments which underpin this material. This article intends to trace the Holy Grail theme from a set of motifs in medieval romance to the modern genre of grail literature and to focus on the resulting interface between literary and popular culture.
Suggestions put forward as to the source and meaning of the "Grail story" include Celtic myth, the Eucharistic rites of Eastern Christianity, ancient mystery religion, Jungian archetypal journeys, dualist heresies, Templar treasure, the descendants of Christ and Mary Magdelene, several actual objects, and any combination of the above. All these positions have adherents who are fierce in defence and detractors who are equally dismissive of these suggestions. The common thread which links these theories is the assumption that the grail story has a single source and that this source has a meaning which is obscured in the romances themselves. The question one might ask at this stage, from the point of view of folklore studies, is whether a series of repeated motifs necessarily implies a common tale and a priori source. In other words, is there a grail problem to be solved or is this simply an artefact of the methodology of grail criticism? Recent academic studies have stressed influences rather than origins and concentrated on the romances as literature rather than as repositories of secrets which the authors do not understand.  However, an earlier, and very influential, stream of romance criticism considered that the origin of romance was the primary question to be answered; and many modern grail studies, however eccentric the research they embody may be, still make use of such assumptions. Many current popular ideas derive from earlier grail scholarship which dates from the 1880s to the 1960s. In order to clarify why this particular story should exercise such a fascination in the popular imagination and in a particular corner of the publishing industry, it would be well to trace earlier research.
The theories discussed in this lecture developed as a by-product of renewed interest in medieval romance, and the middle ages generally, in the nineteenth century. This has to be seen in the wider context of the occult revival of this time, with its tendency to interpret Renaissance philosophy and the innovations of the Age of Enlightenment, such as masonism and Rosicrusianism, as carrying information which, while it could provide personal or cultural transformation, threatened the establishment. Many of these movements were tied in a complex way to the increasing power, and increasingly democratic interests, of the growing bourgeoisie. The appeal of the grail theme, particularly in the early part of the twentieth century, was very wide and broadly European.
Summary of the Grail Romances
One of the frustrations of this material, and a feature which has undoubtedly contributed to the increasingly bizarre theories about its origin, is the fact that no consistent "Grail story" emerges from the several romances in which material appears. …