In the early 1960s, Gérard de Sède, journalist and author, hires a man named Roger Lhomoy as his gardener. The latter, a former guide and guard at the Château de Gisors, claims to have discovered in 1946, after several years of clandestine excavation, a gallery followed by a chapel, which he describes with confounding accuracy: under this 30m-long, 9m-wide, approximately 4.50m-high chapel, he claims to have seen 19 stone sarcophagi 2m long and 60cm wide and 30 precious metal chests, arranged in columns of 10 under the nave of this chapel.
As early as 1960, curator Pierre Bourdil, the town council and Beaux-Arts dispatched a team of archaeologists. In 1961, and again in 1962, the year of the publication of the book Les Templiers sont parmi nous, by Gérard de Sède, excavations were again carried out, without success. The publication of this book unleashes passions and further clandestine excavations, endangering the stability of the edifice. The press and television take up the Gisors affair, to the point that under popular pressure, André Malraux, Minister of Culture, sends the 5th Military Engineers from Rouen to once again undertake excavations in the feudal motte, equally unsuccessful and catastrophic for the stability of the keep.
To this day, only traces of a passage to Gisors castle by Richard de Hastings, Toestes de Saint Omer and Robert de Pirou, three knights of the Order of the Temple, have been established. Nevertheless, the legend continues to fascinate young and old alike.