Did Leonardo give 'Mona Lisa' a younger sister?

She has the most-photographed, most-reproduced, and the most-parodied face in the world. And yet, when many of the six million people who go to visit her each year get to see her “in the flesh”, they find they are strangely disappointed. Her smile is famous, and her eyes are said to follow you around the room, but the best the former Soviet leader Leonid Brezhnev could say about her was that she was “a plain, sensible-looking woman”. So what is so appealing about the Mona Lisa? And what might happen if it were discovered that she has a little sister?

The Mona Lisa that hangs in the Louvre in Paris was painted by Renaissance master Leonardo da Vinci between 1503 and 1519, in oil paint on a panel of poplar wood – or was it? The histories, myths and speculations that wrap around the relatively small (just 77cm by 53cm) painting are enough to fill a Dan Brown novel. Is it a portrait of Lisa Gherardini, the wife of Francesco del Giocondo, or of Isabella of Naples, Caterina Sforza, or even da Vinci himself? Some say the Louvre painting is a fake, a substitution made following the theft of the Mona Lisa by Louvre employee and house painter Vincenzo Peruggia, in 1911. After she disappeared, crowds queued to see the empty space where the painting had hung.

Still others say that the painting was not begun in 1503 and that there are in fact two paintings. The earlier version, known as the Isleworth Mona Lisa (it was in the Isleworth home of art collector Hugh Blaker) was painted on canvas, and now resides in Geneva. It is owned by an anonymous consortium, and in the care of a foundation vice-chaired by Irishman David Feldman, a graduate of Trinity College Dublin.

You might think the idea of a second Mona Lisa would be exciting for the art world, and the putative earlier version is undeniably beautiful, showing a figure in the same pose, but perhaps 20 years younger than the one that hangs in Paris. And yet the Isleworth painting has received an at times hostile and derisive reception.

The Huffington Post’s Simon Hewitt chose to focus on how the chair of the foundation, Markus Frey, was “chomping on a fat cigar” at a recent press conference, and Martin Kemp, emeritus professor of art history at Oxford University, issued statements dismissing the foundation’s claims.

There is a strong sense that the earlier version might be better received if it was to have come fresh from some magnificent English stately home (in fact it did, back in 1913), or if the advisers to the foundation didn’t consist of an unconventional crew, including the Russian chess grandmaster Anatoly Karpov and the world traveller and writer Kildare Dobbs. Feldman describes the foundation and its advisers as a group of friends and like-minded people willing to take the project on. The foundation itself is not-for-profit, although overshadowing this spirit of adventure is the fact that if the painting were to be authenticated, its value would be astronomical.