Who didn't do it?

摘要

Sleuths are stalking the corridors of London's National Gallery. Identifying and preserving paintings is one of the gallery's essential tasks. Is a painting a fake, created to deceive? Was it altered years after it was made in order to conform to later fashions and make it easier to sell? Is it a genuine work later mistaken for that of a more highly valued contemporary? If a picture is a copy, was it made at the same time as the original, perhaps by the same hand? Multiples were not an Andy Warhol invention, although earlier on they took longer to produce.