According to most writers
The whole story of Rennes le Chateau was allegedly started by three confidence tricksters way back in the 1960s: - Pierre Plantard, Philippe de Chèrisey and Gerard de Sède. You may also hear tales about how a resident of Rennes le Chateau, Noel Corbu, made up stories about how the French Curé Abbé Béranger Saunière became exceptionally rich after discovering a secret at his church.
Plantard's interest appears to have been started by a newspaper article written by Gerard de Sède regarding what was termed 'The Gisors Affair' when a Templar treasury was allegedly found by a man who had been a guard at Gisors Castle during the World War II. He had told writer and journalist Gerard de Sède about it when he had come to work on de Sède's pig farm -
Read about it here
The Priory of Sion is (or was) real and this is beyond any doubt. It is also known as the Ordre de la Rose Croix Veritas a definite reference to the Rosicrucian movement, a movement predicted by Nostradamus, a former resident of Alet le Bains just north of Rennes le Chateau.
You will hear that already people were asking for permission to dig at Rennes le Chateau long before Noel Corbu and Pierre Plantard and that you can completely remove all the people previously mentioned from the story and you will still have a story.
You will hear how a man called Jean Luc Chaumeil, a self promoting "expert" on the Solar Temple cult and a man who believes that aliens are running this planet, claims he has proof that the Priory of Sion three contrived to make the whole thing up.
And yet we have
THE CHOLET REPORT
Nothing to do with
Pierre Plantard, Philippe de Cherisey or Gerard de Sède