In 1890, just as the museum acquired The Ambassadors, The Times acclaimed the “faultless” condition of Holbein’s masterpiece, save for “old and perished varnish”. How wrong it was. The conservator Martin Wyld’s detailed record of its 1998 restoration explains its many troubles: as well as the varnish, that gorgeous green curtain we see today was covered in black overpaint; planks forming the support were warped by water damage; and the gaps between them were “filled with cement”. An image of the work after cleaning and before retouching is an alarming sight, especially with extensive losses around the famous anamorphic skull. But retouching has made the picture look better than at any time probably since Holbein first put down his brush.