It has been billed as one of the world's great unsolved mysteries. Ten letters on a marble tablet that, legend has it, could help reveal the location of the mythical Holy Grail.
Many have tried to crack the code which, surprisingly, is not located deep within some catacomb in Jerusalem, but a stately home a short trip up the M6 from Birmingham in Shugborough, Staffordshire.
So far none have succeeded.
However the 258-year-old mystery might be about to be solved.
Canadian codebreaker Louis Buff Parry claims to have unlocked the secret message and plans to explain his theory to the world this weekend.
If he is right, Mr Parry will have succeeded where even codebreakers failed.
Shugborough general manager Richard Kemp said: "We have seen a great deal of Louis's writings on the code and it is the only theory trail we have so far received which we cannot rule out.
"We are very eager to see his full solution and to find out if we really do hold the key to the Holy Grail. "
For those not familiar with the mystery, the code sits beneath a marble relief dubbed The Shepherd's Monument in the 900-acre gardens of the ancestral home of the Earls of Lichfield.
Commissioned by Thomas Anson in 1748, the 20 ft high monument depicts a group of shepherds and shepherdesses contemplating the after-life.
The reason it has been linked to the Holly Grail is because the picture is a mirror-image likeness of a painting by artist Nicholas Poussin.
Poussin was rumoured to be a Grand Master of the Knights Templar and the original painting housed in the Louvre, Paris, was linked to the Holy Grail in Dan Brown's best-selling novel The Da Vinci Code.
It has also been suggested the painting and The Shepherd's Monument both refer to a secret masonic group.
Two years ago the Shugbu-rough estate launched a project to finally crack the enigmatic code in its grounds.
"We got a team of professional codebreakers to look at it," said Russ Gethings, media relations officer at the estate.
"In light of the publicity it gained, we opened up the opportunity for anyone else who had any ideas."
Veteran Second World War codebreakers based at Bletchley Park who cracked the Nazi's Enigma code had a go but failed.
"They believed it may have been connected to a secret masonic cult or a love letter but they couldn't say exactly what it was," said Mr Gethings.
"In the midst of all that there was Louis who contacted us."
The Canadian, who claims to have helped FBI investigators in the wake of the 9/11 terrorist attacks, came across the Shugborough legend while studying Jacobite mysteries and ancient Hebrew tombs.
He is so confident he has cracked the code that he is bringing a US film crew over to the UK with him to film his revelations for a documentary to be screened later in the year.
"He says he has something very exciting to tell us about what he has found out," said Mr Gethings.
"He has chosen Shugborough to reveal what he has found. It is not just about cracking the code, it is about the rest of the monument and the history of Shugborough.
"It will be interesting to hear what he has to say."