The Virgin of the Rocks about 1491 - 1508, Leonardo da Vinci
http://nationalgallery.org.uk/paintings/leonardo-da-vinci-the-virgin-of-the-rocks
National Gallery puts old master back on display after 18-month conservation project
“The conservation work has convinced the gallery’s experts that their painting, a later version of one in the Louvre in Paris, is entirely by Leonardo, one of the greatest geniuses of the Italian Renaissance – and not, as previously thought, partly by his small factory of assistants. The study of the painting has also established that it was never fully finished…”
(http://www.guardian.co.uk/artanddesign/2010/jul/14/leonardo-da-vinci-virgin-restored?intcmp=239)