Exhibition: The heart and skull of humanism

Death is among us, but strife is not inevitable. That's the message of Holbein's 'Ambassadors', now restored by the National Gallery

There's no admission charge to the substantial exhibition devoted to Holbein's The Ambassadors in the Sainsbury Wing of the National Gallery. The free entry emphasises the liberal, enlightened nature of the occasion, which takes us almost to the heart of Reformation humanism. We marvel anew at the meticulous grandeur of Holbein's art while wondering how to place him in the elevated hierarchies of European painting. Almost everyone concedes that Durer was his superior in general imagination and perhaps in intellect. But Holbein was the better painter, as well as being an incomparable portraitist. There's much reason for calling him the best renaissance artist north of the Alps.

How fortunate for England that Holbein was attracted to London. He's never been forgotten, largely because of his connection with the Tudor court, but also because he influenced British art for a surprisingly long time. I would be thrilled to see a complete Holbein retrospective one day. It could be shared between London and Basel, the centre of his European life.

Meanwhile, these are happy days for British admirers of Holbein. In 1992 the National Gallery bought his lovely Portrait of a Lady a Pet Squirrel and a Starling. Earlier this year, we saw four minute but expressive paintings in the Queen's Gallery's show of miniature portraits. If you can get to the Sainsbury Centre in Norwich before 17 December, there are Holbein prints to be seen in "The Age of Durer: German Renaissance Prints from the British Museum"; and now the NG shows off The Ambassadors, newly cleaned and restored.

The picture was painted in 1533 and entered the National Gallery collection in 1890, when it was first cleaned. The restorer, William Dyer, was responsible for some retouching, and also applied varnish to the painting. By the mid-1960s this varnish had become discoloured. Then, in the early 1990s, X-ray photographs showed that Dyer's reconstruction of the elongated skull which is such an important part of the painting had been faulty. It was then decided to remove the 1890 varnish and Dyer's retouchings, effecting "consolidation of the loose paint" and making "restoration of the losses in the paint layer". These procedures were relatively simple: the major difficulty was presented by the skull in the foreground. Understandably enough, Dyer had not fully comprehended the skull's mystery. With the aid of computers, the NG's restoration department was able to make a digital image and to reconstruct Holbein's original work. This is what we see today.

The cleaned and reconstructed picture is utterly convincing. Its reappearance is a triumph. Study of Holbein's mind may now begin afresh, and we must respect Susan Foister's view that "The Ambassadors is in all probability the work by which the artist himself wishes to be known to posterity". Foister, who is curator of early northern European painting at the NG, has included a nice tribute to an earlier scholar, Mary Hervey, who in 1900 was the first person to identify these grave young ambassadors. They were not people of the very highest public distinction, though they were important enough: on the left is Jean de Dinteville, the French ambassador to London in 1533, and on the right Georges de Selve, the Bishop of Lavour and also a diplomat.

Hervey established that these Frenchmen were in London in 1533 to safeguard relations between the King of France and Henry VIII at a time of religious and political uncertainty, and while Anne Boleyn was pregnant - not with a hoped-for boy, but with the future Elizabeth I. So the painting concerned international relations at a high and acute level. Holbein had reason to know about such things. He was a German who had worked in France and (probably) Italy and who had been introduced to England by the Dutchman Erasmus. Acquainted with great men, able to conduct himself at European courts, Holbein was himself a sort of ambassador, not for a country but for art and learning. He must have known of the cruelty, vice and cunning in the French and English courts. Such things enter neither his art nor, apparently, his personality. We know all too little about Holbein's life and beliefs. Few if any of his paintings can be said to convey opinions, with the single exception of The Ambassadors.

In my opinion, The Ambassadors says that death is among us but that political strife is not inevitable, and that the world should be governed by unsectarian religious spirit and learning, not by fat monks and kings with blood on their hands. Holbein must have got his notion of culture from the best of available sources, the conversation and example of Erasmus, the greatest intellectual of his time. Although it is a double portrait of other people, The Ambassadors is a tribute to his spirit.

The portrait of Erasmus himself is important. My only criticism of the exhibition is that Foister has not documented this work, nor discussed it in her otherwise excellent catalogue. I take this painting to be the 1523 portrait, once considered lost, that is the original of a number of variants and copies. Perhaps the National Gallery is shy of calling attention to this rare and incredibly precious work because it has been borrowed from a private collection. The owner is not named. I am not a Holbein scholar, but I worked out his identity in half an hour. Surely other people can and will do the same exercise.

My hope is that the Erasmus portrait will one day join the other Holbein paintings in the National Gallery with which it shares a history. Has it also been recently and expertly cleaned? The picture certainly looks fresh and well cared for. As for The Ambassadors itself: children and other curious visitors will enjoy standing on a nine-inch-high viewing platform, from which the eye compresses the skull into a more coherent image. Personally, I have never found the skull the most memorable part of the painting. Holbein's palette is more remarkable. His colour remains in the eye like a pungent stain. The significant objects on the table - the astronomical instruments, the German hymn-book, and the quadrants - are well explained in Foister's catalogue.

National Gallery, WC2 (0171 747 2885), to 1 Feb.