In the middle of the Louvre’s Mona Lisa room, an endless queue of tourists snakes around a maze of control barriers for a moment’s audience with the world’s most famous painting. What is it about the Mona Lisa that exerts this magnetism? The answer lies in the subject’s mystique.

Popular audiences for art, as for crime drama, cannot resist a mystery and Leonardo da Vinci was a master of the mysterious, partly thanks to his development of sfumato, a subtle way of shading that wreathed his subjects in a veil of smoke.

The Mona Lisa was not yet in existence when, around 1499, Leonardo visited Venice, but he had already painted The Last Supper and his fame went before him. Among the Venetians who fell under the spell of his sfumato was a promising young painter from Castelfranco Veneto called Giorgio Barbarelli (1478-1510). We know from Vasari’s Lives of the Artists that Giorgione, as he was known, met Leonardo and, along with the Florentine master’s suggestive manner of shading, some of his mystique seems to have rubbed off. The artist now at the centre of the Royal Academy’s new exhibition “In the Age of Giorgione” (until 5 June) is himself something of a mystery. We know far less about him than about Leonardo.