‘All Visible Things‘ narrates the fictional tale of the discovery of the diaries of one Paolo del Rosso, assistant to Leonardo da Vinci. Along the way, the book also exploits the complicated saga of the Mona Lisa.

There is fairly compelling evidence that the painting in the Louvre, La Gioconda or the Mona Lisa, is not, in fact, a painting of Lisa del Giocondo, wife of Francesco, a prosperous Florentine merchant.

It is all but certain that Leonardo da Vinci did indeed paint Lisa del Giocondo, probably around 1503. The first true art historian, Georgio Vasari, wrote, ‘Leonardo undertook to execute, for Francesco del Giocondo, the portrait of Monna Lisa, his wife; and after toiling over it for four years, he left it unfinished; and the work is now in the collection of King Francis of France, at Fontainebleau.’

Vasari never met Leonardo and never saw the painting. But he did meet Leonardo’s former assistant and executor, Francesco Melzi.

Further confirmation comes from a marginal note dated 1503, found as recently as 2005 in a library in Heidleberg, comparing Leonardo with the Greek painter, Apelles, noting that he was working on a painting of Lisa del Giocondo.

So far, so straightforward. However this sketch by no less an artist than Raphael, is generally accepted to be of Leonardo’s Giocondo painting, presumably after a visit to Leonardo’s studio by the younger artist, who is believed to have studied under Leonardo for a while. The Giocondo portrait inspired Raphael’s own painting, Girl with Unicorn.

But the Raphael sketch, and the subsequent painting, both have very pronounced columns on either side of the figure.

A close inspection of the Louvre Mona Lisa reveals a hint of what may be the bases of these columns. However, scientific tests have shown that the Louvre painting was never cut down, so never had visible columns.

The Isleworth Mona Lisa has prominent columns, but a rather boring background. Most experts believe that this image too was painted by Leonardo. This painting is increasingly known as the Earlier Mona Lisa.

Then we have the so-called nude Mona Lisas. are from the period of Leonardo and are thought to be by students in his studio, possibly with some contributions from the great man himself. At least one is attributed to Leonardo’s apprentice then assistant, Salaí.

Leonardo spent his final years in France, the honoured guest of the King. In 1517, he was visited by Cardinal Luigi of Aragon. The cardinal’s secretary, one Antonio de Beatis, recorded that Leonardo ‘showed His Lordship three paintings, one of a certain Florentine lady, done from life at the instigation of the late Magnifico Giuliano de’ Medici, another of St John the Baptist, and another of the Madonna and Child placed on the lap of St Anne …’

The first of these is supposed to be the Mona Lisa.

But of course, it cannot be; as Giuliano would not have commissioned a portrait of Lisa del Giocondo. However, it almost certainly is the painting that hangs in the Louvre.

Like pretty much all of the Medici, Giuliano had a wife and several mistresses; almost any one of whom could be the woman in the Louvre painting.

A Milanese artist, Giovanni Lomazzo was a promising painter, until an accident robbed him of most of his sight. He became a Leonardo scholar and devotee and he also knew Francesco Melzi. Lomazzo records that Leonardo painted the Mona Lisa and the Gioconda. Lomazzo was an erudite man, more than capable of distinguishing singular and plural.

Finally, there is the recent analysis of the Louvre painting by Pascal Cotte, which has revealed extensive underpaintings below the image we see. The digital reconstruction (left) approximates the hidden original, which may be no more than an evolving version of the finished work, but the lady does look considerably younger than the other versions.

To recap. The traditional theory is that Leonardo painted Lisa del Giocondo in 1503 and then, for reasons never explained, carried the painting around Italy, tinkering with it until a couple of years before his death, in France, in 1519.

But what if the image underpainting is a likeness of Lisa del Giocondo in a work that was never paid for or handed over, but was then painted over sixteen years later when Leonardo’s patron Giuliano de’ Medici asked for a portrait of his mistress? As luck would have it, Giuliano died before the painting was completed and so, once again, Leonardo failed to collect his fee. The problem I have with this theory is that we have to assume that Leonardo hauled this wooden panel from Florence to Milan and back then to Rome and then to France. Why would he do this? The conventional wisdom is that he was perfecting, not a portrait, but some idealised idea of womanhood, or motherhood, or somesuch. I find this a complete post-rationalisation, with no precedent.

What if the Giocondo portrait was in fact handed over?

It is true that there is no record of any payment from Giocondo: but at the time, Leonardo was short of cash and withdrawing funds from his bank account. He may simply not have deposited the payment. Francesco del Giocondo was a robust businessman and may well have driven a hard bargain in return for his political support. Indeed it has always been a mystery why Leonardo accepted the Giocondo commission at a time when he was turning down much more important and prestigious patrons.

If this is the case, then the Louvre painting is of whichever Florentine lady Giuliano de’ Medici wanted immortalised by Leonardo.

All in all, her smile is not Mona Lisa’s only mystery.