Pierre Athanase Marie Plantard (March 18, 1920 – February 3, 2000) was a French draughtsman best known for being the principal perpetrator of the hoax of the Priory of Sion, which he established to manufacture evidence that he had a legitimate claim to the French throne. This deception later inspired a series of BBC Two documentaries, the 1982 pseudohistory book Holy Blood, Holy Grail and the 2003 novel The Da Vinci Code, among others.

He used an altered surname, Plantard de Saint-Clair, from 1975 onwards. The surname Saint-Clair was added to his own surname on the basis that this was the family name associated with the area of Gisors (in Normandy), a part of France associated with his hoax.

Plantard was born in 1920, in Paris, the son of a butler and a concierge.^[1] Starting in 1937, he began forming anti-Semitic and anti-Masonic associations with the aim of "purifying and renewing France". ^[2] On December 16, 1940 Plantard wrote a letter to Marshal Pétain offering his services to the collaborationist government. His offer was investigated by both the French and German police, which found that Plantard's organization had at most 100 members.^[2] Plantard's phantom associations included the French Union (1937), the French National Renewal (1941) and the Alpha Galates (1942).^[1] Alpha Galates published a periodical called Vaincre (Conquer),^[1] which was frequently laced with anti-semitic, anti-Masonic, and mystical nationalist views. The German authorities had refused permission for Plantard to form the French National Renewal,^[1] and when Plantard disregarded another prohibition in the case of the Alpha Galates, he was given a four-month sentence in Fresnes Prison.^{[citation needed]}

Police reports relating to Plantard's pre-war and wartime activities are contained in the Paris Prefecture of Police, and from this early stage on in Plantard's life it was observed about him that: "Plantard, who boasts of having links with numerous politicians, seems to be one of those dotty, pretentious young men who run more or less fictitious groups in an effort to look important and who are taking advantage of the present trend towards taking a greater interest in young people in order to attract the Government's attention" (Police Report on Plantard's French National Renewal dated 9 May 1941). A Secret Service investigation of him during World War II concluded that his mind was "cloudy", and that he was a fantasist who enjoyed creating right-wing anti-semitic organizations, that were set up like medieval orders of chivalry.

In 1951, Plantard married Anne Léa Hisler (1930-1970). They moved to the town of Annemasse in south-east France, near the border with Switzerland.^[1] In 1953, Plantard was accused of selling degrees of esoteric orders for exorbitant sums^[1] and was given a six-month sentence for fraud.^[3]

On May 7, 1956, Plantard and others legally incorporated in the town of Annemasse a new group called the Priory of Sion. The Priory was devoted to the support of politicians working to build low-cost housing in Annemasse.^[1] It published a magazine named Circuit.^{[4] [4]}The "Sion" in the name did not refer to Jerusalem but rather to a local mountain, Montagne de Sion, where the order intended to establish a retreat center.^[1]

Influenced by the hotelier Noel Corbu who claimed in 1956 that a treasure had been previously discovered in the area by the 19th century occupant of his property, Father Bérenger Saunière, Plantard further embellished the story by claiming that this treasure included parchments that substantiated Plantard's descent from Dagobert. Plantard began writing manuscripts, and produced forged medieval "parchments" (created by his friend, Philippe de Chérisey) with the claim that Saunière had supposedly discovered these documents whilst renovating his church in 1891. These documents purportedly showed the survival of the Merovingian line of Frankish kings. Plantard manipulated the story of Saunière's activities at Rennes-le-Château in order to "prove" his claims relating to the Priory of Sion. In 1966, he also planted arcane home-made documents in the Bibliothèque nationale in Paris. These documents, the so-called Dossiers Secrets (Secret Files), purported to corroborate the Priory's version of history. They were a remarkable collection of genealogies going back over a thousand years, all painstakingly created by hand over a period of months, with nothing more than a cheap stencil kit to produce the family trees and crests.

During the early 1960s, Plantard put himself forward as a Merovingian claimant to the throne of France, descended from King Dagobert II. This position was apparently influenced by an article by Louis Saurel that he had read in the French magazine Les Cahiers de l'Histoire Number 1 (1960). Louis Saurel's article had argued that Dagobert II was the last effective independent Merovingian King before the "Mayors of the Palace" began taking control. There is no prior evidence that Plantard or his family claimed descent from the Merovingian dynasty, and the format of Louis Saurel's 1960 article in Les Cahiers de l'Histoire was later copied in a 1964 Priory Document ascribed to "Anne Lea Hisler" entitled "Rois et Gouvernants de la France". Plantard in reality was the son of a butler and a cook, who had no recorded links to the Merovingians.

This period of Plantard's activities coincided with his meeting French author Gérard de Sède, who with the collaboration of Plantard published in 1962 the book Les Templiers sont parmi nous, which related to the Gisors story that was begun by Roger Lhomoy (Lhomoy was de Sède's pig-farmer during this time). The book seems to have been the genesis of what was soon to become the popular version of the Priory of Sion, with the well-known ingredients – Godfrey of Bouillon, the Knights Templar, and so on. All of this can be easily proved to be historical fiction because the various claims as found in the Priory Documents never existed before the early 1960s in any shape or form, and cannot be substantiated from the known historical records.

Furthermore, letters in existence dating from the 1960s written by Pierre Plantard, Philippe de Cherisey and Gérard de Sède to each other confirm that the three were engaging in an out-and-out confidence trick. The letters describe schemes on how to combat criticisms of their various allegations, and how they would make up new allegations to try and keep the whole thing going. These letters (totalling over 100) are in the possession of French researcher Jean-Luc Chaumeil, who has also retained the original envelopes, and the originals of the forged medieval documents that were reproduced in the book Le Tresor Maudit de Rennes-le-Chateau, a collaboration of Plantard and Gerard de Sede. Jean-Luc Chaumeil during the 1970s was part of the Priory of Sion cabal and wrote books and articles about Plantard and the Priory of Sion before splitting from it during the late 1970s and exposing Pierre Plantard's past in French books. The Priory, Plantard claimed during the mid-1960s (but not before, and certainly not in 1956), was a secret inner circle of the Templars: It had survived the extinction of the original order, and had been manipulating events in Europe over centuries to keep alive the "rightful" Merovingian royalty.

In 1979, Plantard met with Henry Lincoln and others, and claimed that he was the current Grand Master of the Priory of Sion.^{[citation needed]}

In 1982, authors Michael Baigent, Richard Leigh and Henry Lincoln published Holy Blood Holy Grail. It became a bestseller, and publicized Plantard's Priory of Sion as a "real" organization. The book also expanded upon the story though, claiming that the Merovingian line of kings had actually been descended from Jesus Christ and Mary Magdalene, and that the purpose of the Priory (and its military arm, the Knights Templar) was to protect the secret of the holy bloodline.

Plantard was reportedly horrified by this embellishment, saying that it was sacrilegious. He rejected the claims during the late 1980s when he revised the mythological pedigree of the Priory of Sion, claiming it had nothing to do with the Knights Templar, that the "Dossiers Secrets" were written under the influence of LSD, and that the Priory of Sion had in fact been founded in 1681 at Rennes-le-Château by the grandfather of Marie de Negri d'Ables. This revised version of the Priory of Sion had been influenced by the opening of the "Sauniere Museum" in Rennes-le-Chateau in May 1989.

In a 1989 issue of Vaincre, Roger-Patrice Pelat was named as a grandmaster of the Priory of Sion. Pelat was a friend of the then-President of France François Mitterrand and center of a scandal involving French Prime Minister Pierre Bérégovoy. In October 1993, the judge investigating the Pelat scandal visited Plantard's home to question him and have his house searched. The search failed to find any documents related to Pelat. After also interviewing Plantard's son Thomas, the investigation of Plantard's connection with Pelat was closed.^[5]

After this, Plantard lived in obscurity until his death on 3 February 2000 in Paris.

Thomas Plantard de Saint-Clair (born 1970) is the son of Pierre Plantard, the principal figure behind the creation of the Priory of Sion. Thomas Plantard de Saint-Clair was alleged to have taken over as Grand Master of the Priory from his father, according to a proclamation made by Pierre in 1989. At the time he was managing editor of the Priory's journal Vaincre. He has kept a very low profile since his father's death.^{[citation needed]}

• Second part of the interview of Jean-Luc Chaumeil where he mentions his discovery of the bewitched hill and the owner of the abbé's estate, Henri Buthion, as well as his tumultuous relations with Pierre Plantard (Priory of Sion)!