Thierry Jean-Pierre was the Judge who in 1993 investigated Pierre Plantard’s claim that Roger-Patrice Pelat was the Grand Master of the Priory of Sion, remanding Plantard in custody for 48 hours on 19 October and searching his home (perquisition), and questioning him over the matter on a second occasion on 15 November – as reported in Le Point dated 8 January 1994

The claim that Roger-Patrice Pelat was Grand Master of the Priory of Sion was first given in a Priory circular reproduced in Les Cahiers de Rennes-le-Château, Tome IX, 1989 (“Félicitations M. Plantard!”). Pelat's name appeared on a Grand Masters List in Vaincre N° 3, September 1989, page 22, his alleged tenure of the position 1985–1989

Le Point N° 1112, January 1994