An interesting collision on West 57th Street in New York; the anonymous graffitist is saluting Norman Rockwell’s words while at the same time obliterating them. But this isn’t a straightforward high-vs-low tussle. For many years, Rockwell was held at arm’s length by the art world, the cosy sentimentality of his Saturday Evening Post covers outshining his sometimes radical intent; street art, meanwhile, has become big business. Would Rockwell have retaliated? And would his retaliation have been art?