Erotic masterpiece linked to Leonardo goes on show

The two young ladies could not be more different. The Mona Lisa is aloof, self-contained and self-possessed, her right hand clasped on her left wrist, all her sensuality concentrated in the secretive vitality of the eyes and the famous small smile. It's the allure of a roaring fire on a winter's day.

Mary Magdalene's is the sensuality of hot summer. Her hair falls loose on her shoulders, her crimson robe is thrown open exposing her breasts, her right hand tugs at the flimsy veil cladding her stomach. When the fingers of her left hand open the rest of the robe will drop away, exposing her completely. It's a pose of erotic titillation, and there is something hypnotic about her gaze, directed at a person unseen off to the artist's right.

The Mary Magdalene has long been attributed to Leonardo's pupil Giampietrino. But Carlo Pedretti, the Leonardo expert at the University of California at Los Angeles, who is co-curating the exhibition, said: "Because of its very high quality, I am inclined to believe that it is much more than a supervision of the student by the master."

The painting has not been seen in public since a brief airing in the United States in 1949. A black and white photograph of it was taken in the 1920s. Professor Pedretti, who is 77, tracked it to a private collection in Switzerland. He wants the picture to undergo an infrared reflectogram, which will reveal if there are sketches underneath the paint, because, he says, Leonardo's sketches are easy to identify. "One extraordinary thing," he said, "is that it is painted on an intact wood panel, just like the Mona Lisa".