I read and enjoyed the Holy Blood & The Holy Grail (and its follow-up whose name I forget).
It seems though that many of the claims made about the 'Priory Of Sion' have been shown to be flimsy at best. But today I see the story still has legs: "Indiana Jones meets The Da Vinci Code in tiny French village" http://goo.gl/rDgNk "...researchers have revealed the entrance to a cave they insist contains King Solomon's gold, and possibly the Holy Grail". (Hey Barry - you're into the Cathars and all that stuff. And not just in this life, no?. I wonder what you make of the Rennes-Le-Chateau saga?)