The article begins with a brief survey of what is known of the picture's history. A section follows, which is concerned with the condition of the picture (National Gallery No. 181) prior to cleaning. The x-radiographs are discussed, which suggested that at one time the picture may have had a rounded top, subsequently cut and made into a rectangle by the addition of corners. The x-ray mosaic also showed evidence for alterations in the composition at the bottom of the picture, in the region of the parapet. Details of the cleaning tests are given, which show, amongst other things, that the drapery of S. John was not original and that part of the parapet was false. Following a section on the restoration and framing, the author suggests possible explanations for the alterations that were found. There are illustrations of the panel before, during, and following cleaning and restoration, as well as an x-ray mosaic.