An artistic style that can be plagiarised is one that can be the subject of copying. As we know from the studies of Hans Belting (1990) and others, style, as we understand it, was, if not invisible, then at least an unobservable during late Middle Ages. This invisibility can be tested with the help of an example, taken from Alexander Nagel,1 of a painting, brought home to Cambrai from Rome by a Flemish prelate in 1440.