1. When he died, he left some works to Salai, while his more recent companion Francesco Melzi inherited his notebooks.

2. Salai, real name Gian Giacomo Caprotti, an effeminate young artist who worked with da Vinci for 25 years, is thought to have served as a model and muse for several of his paintings.

3. Salai and da Vinci worked together for 25 years and is believed to be the inspiration behind several of the Renaissance artist's works.

4. Salai, an effeminate young artist who worked with da Vinci for 25 years, is thought to have served as a model for several of his paintings.

5. As well as looking like Salai, the Mona Lisa gives even more clues to his influence, says Vincenti.

6. He said: "Close examination of a high-quality digital copy of the portrait had revealed an L for Leonardo and an S for Salai."

7. "Close examination of a high-quality digital copy of the portrait had revealed an L for Leonardo and an S for Salai." A romantic gesture?

8. Close examination of a high-quality digital copy of the portrait had revealed an L for Leonardo and an S for Salai.

9. "Close examination of a high-quality digital copy of the portrait had revealed an L for Leonardo and an S for Salai," he said.