They're calling it the 'real Da Vinci Code' after author Dan Brown's bestselling Leonardo da Vinci-inspired mystery novel - but the latest revelation to grip the art world is anything but fiction.
The code can be found in the eyes of none other than Da Vinci's masterpiece, the Mona Lisa, famed for her ambiguous smile and mystery identity. According to expert Silvano Vinceti, the letters "LV", likely the artist's initials, are painted in black on green-brown in the Mona Lisa's right pupil.
Yet even more intriguing is the apparent hidden message hidden in her left eye. The letters read "B" or "S", or possibly the initials "CE", Vinceti told the Guardian.
Vinceti suggests that these mystery initials are a clue as to the Mona Lisa's real identity - a revelation that could discredit the theory that the model was Lisa Gherardini, the wife of a Florence merchant.
Da Vinci loved his codes and symbols as ways of getting messages across - yet he isn't the only painter to have hidden things in his art. A number of hidden gems have cropped up on the markets in recent years, often with valuable results. Here are some of our favourites...
The censored 'Female figure study' by John Constable
This piece was auctioned at Bonhams in April of this year, with a 1972 cutting from The Times newspaper describing how the piece was discovered in an album by buyer William Darby, hidden underneath an invitation to a Royal Academy dinner.
He suspected that the drawing may have been covered up by a previous Victorian owner of the album because of its 'sensitive' nude subject matter. The work appeared at Bonhams estimated at £4,000-6,000 - but finally sold for £24,000.
A discovery before breakfast... Jackson Pollock's 'signed' Mural
Jackson Pollock's 1943 work Mural was key to cementing the young artist's reputation as a painter of international importance. But, like Da Vinci, the abstract impressionist also apparently had a fondness for hiding things - sometimes to the extent of duping the world's leading art experts.
Henry Adams is an art historian who has written a book on Pollock's life, but even he didn't spot the signature hidden in Mural. Instead, his wife saw it while glancing at the piece over breakfast. "The characters are unorthodox, ambiguous and largely hidden" Adams wrote in Smithsonian magazine.
"I was flabbergasted. It's not every day that you see something new in one of the 20th century's most important artworks" he wrote - although there is dispute among Pollock experts over Adams's claims. Mural is now owned by the University of Iowa, and valued at $140m.
Sir Alfred James Munnings, depicted in a
Was it a love triangle? The hidden Sir Alfred James Munnings...
The acclaimed early-20th century artist Dame Laura Knight apparently found fellow painter Sir Alfred James Munnings tremendously impressive when they first met. Her husband, Harold Knight, was less enamoured with him perhaps because of this interest...
So it's possible to read various metaphors and comments into the fact that a complete oil painting of Munnings by Harold Knight has been found hidden behind the canvas of Le Carnival by Laura Knight.
Depicting the charismatic Munnings reading, perhaps to an audience, the work appeared at Bonhams with an estimate of up to £50,000. In the end, bids pushed its value all the way up to £115,250.
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