December 1953 - June 1954
When BBC2 showed the “Timewatch” documentary The History of a Mystery for the first time on 17 September 1996 the following information was given about Pierre Plantard:
Under French Law every new Club or Association must register itself with the Authorities - and that's why there's a dossier here [Saint Julien-en-Genevois] showing that a Priory of Sion filed the proper forms in 1956... The dossier also notes that the Priory's self-styled Grand Master Pierre Plantard - who is central to this story - has done time in jail.
No filming was done in the town of Saint-Julien-en-Genevois where the 1956 Registration documents of the Priory of Sion are held – but one of the team did do some on-the-spot research and after signing-in on Tuesday 20 June 1995 in the Sub-Prefecture, accessed the Hall of Records and pulled out all the relevant drawers, eventually consulting the file containing the Registration documents of the Priory of Sion. In the File the researcher discovered a letter dating from 1956 written by Léon Guersillon who was the Mayor of the nearby town of Annemasse at the time (and where Plantard lived during the 1950s), and transcribed the following passages from it:
Its researchers too also consulted the 1956 File on the Priory of Sion containing the Registration documents, there witnessing Léon Guersillon’s letter referring to Plantard’s 1954 prison sentence, thus verifying the account given in The History of a Mystery documentary of 1996.