A Canadian cryptologist believes part of the Holy Grail lies in or close to a Staffordshire estate.
The inscription on the Shepherd's Monument reads D OUOSVAVV M
Louis Buff Parry has spent two years studying letters etched on a monument in Shugborough which are widely believed to be some sort of code.
Two years ago experts from Bletchley Park decided the letters, rumoured to be linked to the Grail, were a message from an 18th Century Christian sect.
Mr Buff Parry said it is a message the Grail is buried nearby.
The marble tablet is in the grounds of the Shugborough estate, near Stafford, and was owned by the Anson family, ancestors of the current Earl of Lichfield.
It was commissioned in 1748 by the then earl, Thomas Anson, and features a carved image of a Nicholas Poussin painting with the letters D OUOSVAVV M inscribed below.
Mr Buff Parry believes a Holy Grail stone was captured in France and brought back to Shugborough in 1746 by Admiral George Anson.
Shortly afterwards, the family commissioned the tablet which they encoded with the stone's location.
Mr Buff Parry believes the D and the M stand for 1500 in Roman Numerals and refer to the 1,500th verse of Genesis.
The lack of a full stop after the final V means the part of the code should be read from right to left, spelling VVA - a word which means bloom or offshoot in Hebrew.
Other letters refer to the name Joseph, leading to the phrase The Bloom of Joseph as in Genesis verse 1,494. He said in the bible that phrase means the stone the builders forgot.
He said: "I believe it is very likely that at least one of the stones will be eventually found here."
The Bletchley experts had different theories about the code
Richard Kemp, general manager of the estate, said Mr Buff Parry had managed to pin point the search for the Holy Grail from all over the world down to the estate.
"I think this new development will act as a platform for others to work from," he said.
"I have read every theory that has ever been written and this is the most exciting because, in my mind, I cannot find a question that he cannot answer."
Mr Buff Parry is to talk about his theory at a code breaking and Holy Grail weekend at the estate.