A look beyond the smile of arguably the most famous portrait in the art world, two-and-a-half feet tall and about 50 years old, which hangs behind plate glass in the Louvre in Paris. Painted by Leonardo Da Vinci, La Gioconda, better known as the Mona Lisa, is the most idolised and most abused woman in the history of art. But what lies behind that famous smile? First broadcast in 1981