Marten van Heemskerck, 'The Virgin and Saint John the Evangelist', about 1540

A youthful Saint John the Evangelist supports a grey-faced and anguished Virgin Mary. This is one of two shutters from a triptych (a painting in three sections), which presumably flanked an image of the suffering Christ, which is now lost.

The back is painted too, and shows a bishop holding an open book, standing above a shield with a coat of arms (for the coats of arms, see The Donor and Saint Mary Magdalene). Two keys hang from a cord on his left wrist. There appear to be two standing figures on his morse (the clasp on his cope) but the detail is difficult to make out. A veil is tied to his crosier. Aside from the shield beneath his feet, everything is rendered in tones of black, grey and white.

The bishop’s identity remains uncertain. He may be Saint Peter, to whom Christ metaphorically gave the keys to the kingdom of heaven, and who, as first bishop of Rome, might appropriately be depicted wearing a mitre on his head. He was, however, normally shown bearded and wearing a grander papal tiara. The only other male saint depicted holding two keys seems to have been the seventh-century Saint Riquier, but he was an abbot, not a bishop. Saint Servatius was a bishop, and while one of his emblems was a key – he was patron of locksmiths – he was shown with only one, and was often accompanied by a dragon.

The Virgin must have looked as if she was kneeling on the original frame, as did the donor in the other panel. The current frames are old, but not original. They bear the marks of hinges, which were almost certainly in place when the wings were still fixed to the lost central panel, but their carpentry is rather crude: before treatment in 1986–7 neither panel fitted well into its frame. The unpainted edges show that the original frames were engaged (made from the same piece of wood as the panel) and were secured with pegs that fitted into holes in the unpainted edges. It remains to be discovered why the original frames were removed and replaced, apparently when the panels still formed part of a triptych.