Was da Vinci's lover the face of Mona Lisa?

Maike Vogt-Luerssen says 17 years of research have lead her to conclude that the Mona Lisa portrayed the love-sick Duchess of Milan, and not the wife of a Florentine merchant, as the Louvre, where the picture hangs, insists.

She believes the notoriously enigmatic smile is the hint of the noblewoman’s passion for the painter - and that she may have been Leonardo da Vinci’s lover.

The widely accepted story of the painting, also known as La Gioconda, dates back about 500 years. It is sourced to the Renaissance biographer Giorgio Vasari, who gave an early account of da Vinci’s life, writing about 100 years after the painter was born in 1452.

Mona Lisa was said to be short for Madonna Lisa, who was the wife of the Marquese del Giocondo, a Florentine merchant. Her husband commissioned the painting out of love, it was said. "This work is executed in a manner well calculated to astonish all who behold her," Vasari wrote.

The Louvre itself has long endorsed Vasari’s account. But Ms Vogt-Luerssen believes the portrait that Vasari is describing is not the Mona Lisa. For one thing, he talked about it being an unfinished work. "Everything the Louvre says is without proof and there were always art historians who opposed this," she says.

Isabella of Aragon was only 17 when she married her cousin, an abusive alcoholic who was also said to be impotent. Her mother had recently died. But she was well-known as a friend of da Vinci, who for more than a decade worked as painter to the Milanese court.

History records that her husband, Gian Galeazzo II, Maria Sforza, was deposed from the duchy by his uncle, Ludovico, who held him in prison until his death. Da Vinci had entered Ludovico’s service in 1482.

The Mona Lisa was widely recognised as a superior piece, but da Vinci never sold it. He is thought to have painted it between 1503 and 1506. He carried it everywhere in his subsequent travels, finally taking it with him to France, where he died.

"This was a love story," Ms Vogt-Luerssen told an Australian newspaper. "But it was most difficult because she is high and mighty and Leonardo was a painter. It wasn’t allowed."

Ms Vogt-Luerssen is an amateur historian who now lives in Adelaide. Her book, Who is Mona Lisa? In Search of Her Identity, created a stir when it was published in Germany.

She says the clues to the Mona Lisa lie in the painting and also in diaries and other contemporary records. The subject’s heavy mourning garb and the absence of jewellery reflect the death of her mother the year before.

Ms Vogt-Luerssen says that on the bodice of her plain brown dress she wears the symbols of the dynasties of Sforza and Visconti, into which she married. "Why is she looking so sad? She married at the end of 1488 when she came to Milan but she had a big problem. She married her cousin, a beautiful man, but he was a drinker and he had problems with impotence."

She says contemporaries describe a spirited woman who was always weeping because her husband beat her.

A different theory on the Mona Lisa’s enigmatic smile appeared in New Scientist magazine this week. It suggested that interference in our eyes - like TV "snow" - makes us believe she’s smiling one minute and not the next.