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:

...in our archives we have a note from the I.N.S.S.E dated 15 December 1954 advising us that Monsieur Pierre Plantard was sentenced on 17 December 1953 by the court in St. Julien-en-Genevois to six months imprisonment for a ‘breach of trust’ under articles 406 and 408 of the Penal Code.

On 30 April 2006 CBS News showed its “60 Minutes” magazine programme that did a feature on Pierre Plantard and the Priory of Sion, following the enormous success of Dan Brown’s 2003 novel The Da Vinci Code. The documentary did on-the-spot research in France and managed to film inside the Sub-Prefecture of Saint-Julien-en-Genevois.

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.

This comes from the 2006 “60 Minutes” news item about Pierre Plantard and the Priory of Sion:

After the War Plantard moved to the small French town of Annemasse – in 1953 he was given a six month sentence for fraud

The late Jean-Luc Robin (1949-2008) and former member of the Fringe Community in Rennes-le-Château gave an interview in 2004 for the DVD release Inside The Da Vinci Code and had this to say about Pierre Plantard:

He [Plantard] used to come to Rennes-le-Château but many years ago – so I only appeared on the scene about 10 years ago and he had already gone since – I see he was jailed, he was jailed - he was a great inventor of the whole [Priory of Sion] story…