How to spot a perfect fake: the world’s top art forgery detective

Modern forgers have kept pace with the techniques that attempt to trap them. Art forgeries are of such a high quality that even Sotheby's, one of the world's largest brokers of fine art, has trouble weeding them out. Samanth Subramanian tells us about James Martin, the fraud-busting expert Sotheby's brought in to spot these perfect fakes.