Leonardo da Vinci portrait lost for 500 years found in private vault in Switzerland

Researchers in Italy claim to have unearthed the portrait of a noblewoman by Leonardo da Vinci which has been lost for 500 years and features the same enigmatic smile as his Mona Lisa.

The portrait of Isabella D'Este, which carbon dating suggests was painted around the start of the 16th century, has been found in a vault containing a private collection in Switzerland and has been verified by a leading authority on Da Vinci.

"There are no doubts that the portrait is Leonardo's work," said Carlo Pedretti, an emeritus professor of art history at the University of California.

If acknowledged as genuine - and if experts concur it was painted before the Mona Lisa - the portrait could shake up academic studies of one of the world's most famous paintings.

The 61cm by 46.5cm portrait, which uses the same pigment in the paint and the same primer used by Leonardo, is the completed version of a sketch he made of D'Este, which, like the Mona Lisa, hangs in the Louvre in Paris.

The unnamed family which owns the portrait, and asked for it to be analysed, has kept a collection of about 400 paintings in Turgi, Switzerland since the start of the 20th century. In a letter to the owners, Pedretti stated he was convinced Leonardo had painted the portrait's face, while two of his assistants painted the palm leaf the subject is holding.