A painting of the Mona Lisa hangs above a fireplace in a London flat in the 1960s. Is this picture not only by Leonardo da Vinci, but also an earlier version of the world famous portrait that hangs in the Louvre Museum in Paris?
And the scientific evidence? Professor Kemp says the information offered by the Mona Lisa Foundation is only “permissive” and, while not ruling out the Earlier Mona Lisa from being by Leonardo, it certainly doesn’t prove that it is.
However, he adds “examination by infrared and other technical means, shows that it [the Louvre Mona Lisa] underwent an evolution, as all Leonardo’s pictures did.
“The infrared examination of the Isleworth Madonna [as Earlier Mona Lisa is also known] is just tediously exact and is clearly the kind of drawing that’s made when you’re copying something rather than generating it.”
Professor Isbouts, however, is critical of Professor Kemp’s analysis in part because “Martin has never seen the work, and that’s the beef that David and Joel [Feldman of the Mona Lisa Foundation] have, and I think it’s a legitimate beef.”
In response Professor Kemp replies: “The old canard that you always have to go and see it in the original, even if it is a bit of rubbish, is not sustainable, particularly with modern imaging techniques. And some of the high quality digital images, you can actually see more in them than you can see in the painting, even with a magnifying glass.”
The experts may disagree about the evidence, but has all the material been presented clearly?
The BBC has seen sections of a pre-production copy of a book – written by several contributors but edited by Professor Isbouts – about the Earlier Mona Lisa, called “Leonardo Da Vinci’s Mona Lisa: New Perspectives”.
One of the contributors claims that in the final, published, version of the book, sections of his text seem to have been removed. He claims many of the deleted passages appear to be ones that are not helpful to the theory that the Earlier Mona Lisa is by Leonardo.
Professor Isbouts denied this: “I definitely edited some segments because I’m the editor. And in some cases there were passages that I don’t think were scholarly defensible. I was just trying to keep the thrust of the argument intact – I certainly didn’t remove anything of a contrarian nature. There were two chapters that were simply way too long.”
He later emailed the BBC, having contacted the contributor to see which passages he was concerned about, and said: “We are working on the final version of the book, in hardcover, so we can still make some corrections within the available word count.”
A Mona Lisa, but no money
One thing supporters of the theory that the Earlier Mona Lisa is by Leonardo da Vinci have to explain is where the painting came from.
It suddenly emerged in 1913, when Hugh Blaker bought it from a manor house in Somerset.
“Blaker believed he was on to something,” says Professor Robert Meyrick of Aberystwyth University who studies the life of the art dealer.
Despite successfully tracking down genuine paintings by artists such as Rubens, Velázquez, El Greco, Manet, Constable, and Turner, Blaker’s business dealings often went badly, and he never managed to sell his Mona Lisa.
“It was like a like a catalogue of failures really, despite his best efforts,” says Professor Meyrick, of the man who struggled financially in later life.
Following Blaker’s death, the painting ended up in the hands of an eccentric art dealer called Henry Pulitzer – he believed the Earlier Mona Lisa was actually more impressive than its more famous counterpart in the Louvre.
But Pulitzer needed some help in trying to convince the world that they were both by Leonardo.
A helping hand
“He started running out of money to promote it, because he wanted to prove that it was a real Leonardo da Vinci,” Andrew Gilbert says.
His family knew Pulitzer, bought pictures from him, and sold him some too.
They have shown the BBC a series of documents which they say shows the family bought a 25% share of the painting in 1964. About a decade later Pulitzer locked the portrait in a Swiss bank vault, and following his death, it eventually ended up in the hands of the international consortium in 2008.
The Mona Lisa Foundation vehemently disagrees with the Gilberts’ claim, its president telling the press in July their case is “ill-founded and has no merit”.
But the family have pressed on and called in the “Sherlock Holmes” of the art world to help.
“Well, I guess I don’t mind it,” Christopher Marinello, CEO and founder of Art Recovery International, says about his nickname.
“We’ve recovered about $510m (£400m) worth of art over the years. We’re still heavily involved in some of the biggest cases going on right now in the art world, and we’re proud of that.”
But what does he think of the claim that the painting in this case might be by Leonardo da Vinci?
“I honestly don’t care about any of it,” he replies. “As far as I’m concerned, this is a simple matter of clients who have a contract of purchase for this painting, whatever it may be.”
It’s thanks to Mr Marinello that the Gilberts (who say they themselves are not sure if the portrait is a real Leonardo) began legal proceedings against the Mona Lisa Foundation in Italy while the painting was being exhibited in Florence.
The Caribbean connection
Ahead of this week’s court hearing, the Gilberts’ lawyer, Giovanni Protti, said this is the “most tricky and interesting case I’ve ever worked on”.
“We’ve had to service a writ of summons to a lot of countries all over the world.”
And that work has borne fruit. After a court hearing on Tuesday, Karen Gilbert says: “The Mona Lisa Foundation declared in front of the judge that Mona Lisa Inc in Anguilla was the owner of the painting.”
There is nothing to suggest such an arrangement implies any wrong-doing by the foundation or the international consortium, but the Caribbean island, which is a British Overseas Territory, is known for its discreet way of doing business.
“We’re chipping away at it,” Karen says. “We know therefore that we’re on the right track with the research that we’ve done.”
This doesn’t establish that the Gilbert family do own a share in the portrait, but it is the first time that the Mona Lisa Foundation have disclosed who the owner is.
In response to Tuesday’s hearing, the Mona Lisa Foundation’s lawyer, Marco Parducci, says: “The Mona Lisa Foundation can neither confirm nor deny the claim, by virtue of the legal obligations it has towards the owners, unless it is explicitly requested by the judicial authority.”
He adds that the Gilberts’ claims suggest they are motivated by “economic interest and the desire to damage the foundation” and the next hearing in March will show “that there is no case”.
The legal battle will roll on, but what would Leonardo, the great renaissance scholar, make of puzzles like the Earlier Mona Lisa and the myths that surround his work, 500 years after his death?
“Oh, he would be incredibly pleased,” laughs Professor Kemp. “He was interested in fame.
“He would have cringed at some of the nonsense, but the fact that his name is the best-known name in the history of culture? Yes, he’d be very pleased.”