Why I think Mona Lisa became an icon

I was seven when I first saw the Mona Lisa . My mother had programmed me to be impressed: her eyes follow you everywhere and her smile is enigmatic. I did as I was told and was dutifully in awe.

Millions are. Art historians, poets and admirers have tried to explain the commanding place that the Mona Lisa has in our cultural life with reference to criteria intrinsic to the work. There is something, they argue, inside the painting that speaks to us all, that unleashes feelings, emotions and recognition.

I think one should avoid succumbing to the charm of a myth, to the idea that, inside every masterpiece that has remained alive for centuries, something imponderable speaks to us as it has spoken to the previous generations. A work of art with impeccable high culture credentials winds up also being the most popular. A survey conducted in Italy for my book showed that 85.8 per cent thought the Mona Lisa was the world's best-known painting, followed, by Van Gogh's Sunflowers (3.6 per cent) and Botticelli's Spring (2 per cent). This is not entirely the result of modern hype.

Mona Lisa was regarded as a masterpiece by Leonardo da Vinci's contemporaries. They were struck by its innovatory pose: she sits presenting a three-quarter view while the face looks directly at the viewer, defiantly. The strange landscape background is constructed vertically, the depth being obtained by "reading" it from top to bottom, like a Chinese painting. The chiaroscuro and the sfumato add depth and movement. As a result, it was widely copied. But this is not sufficient to transform a "normal" masterpiece into a global icon.

The Mona Lisa had the good luck to end up in the collection of the king of France instead of the peripheral court of some minor aristocrat.

After the revolution, it was moved to the newly created museum at the Louvre and found itself at the centre of Europe's artistic world. Then the Romantic intelligentsia focused on the Mona Lisa as the archetypal femme fatale and invented the mysterious smile.

The concept was further elaborated by Walter Pater in his famous passage on the Mona Lisa: "She is older than the rocks among which she sits; like the vampire, she has been dead many times, and learned the secrets of the grave." By then the cult of Leonardo - the quintessential Renaissance Man equally at home in the arts and sciences - was in full swing. The universal Woman could only have been painted by a universal genius.

To bring the painting to the attention of the new popular press, a startling event was required. As if on cue, it was stolen in August 1911, obtaining the required worldwide coverage. By the time it was recovered, in 1913, the Mona Lisa had become the best-known Renaissance masterpiece ever - ready to be sent up by the Dadaist movement.

In 1963, this Italian painting was sent to Washington to represent French culture, and in 1974 it went to Japan. Since then it has been used in more than 1,000 adverts.

A complex historical process, not a single cause, is behind the present status of the Mona Lisa as a global icon. In this, everyone has had a role to play: from Leonardo and the intellectuals who wrote about her smile to all those who sang her, drew her, distorted her, made fun of her and all the solvers of enigmas and all those who exploited her fame not realising or caring that, in so doing, they were adding to it.

The story of the Mona Lisa demonstrates that one object can be both a classic of Western art and pop, hip, and cool.

Donald Sassoon Professor of comparative European history, Queen Mary College, University of London

Mona Lisa: The History of the World's Most Famous Painting was published this week by HarperCollins, price £16.99.