In 1533, Hans Holbein the Younger painted two French diplomats at the court of Henry VIII. The painting, now called The Ambassadors and hanging in the National Gallery in London, is two metres by two metres, in oil and tempera on oak panel. The two men stand on either side of a tall double-shelf cabinet covered in instruments, books, and globes. The floor is patterned in a geometric mosaic copied from the Westminster Abbey pavement. Between their feet, across the lower third of the painting, is a smudge of grey-brown paint.

From the centre of the painting, the smudge looks like a piece of damage or an unfinished section. From the right side of the painting, viewed from below at floor level, the smudge resolves into a perfectly drawn human skull. The technique is called anamorphosis, and Holbein's deployment of it here is the most technically accomplished use of the device in the sixteenth century.

What the Painting Shows

The two sitters are Jean de Dinteville, on the left in pink satin and ermine, and Georges de Selve, on the right in a long black robe. De Dinteville was the French ambassador to the English court in 1533. De Selve, his close friend, was the Bishop of Lavaur, on a visit to London at the time of the commission. Both men were in their twenties.

The objects on the cabinet between them are a careful inventory of contemporary intellectual life. On the upper shelf: a celestial globe, a portable sundial, a quadrant, a torquetum (a complex astronomical instrument), and a polyhedral sundial. On the lower shelf: a terrestrial globe, a German hymnal (Walther's, 1524) open to two specific hymns associated with Lutheran reform, a lute with a broken string, a case of flutes, an arithmetic textbook, and a German hymnbook.

The objects are not decorative. Each one carries specific symbolic weight. The lute's broken string and the partly open hymnbook reference the religious schism that was tearing Europe apart in 1533: Henry VIII had broken with Rome that same year. The astronomical instruments reference the new mathematical understanding of the universe. The arithmetic textbook references the rise of commercial culture.

The Skull

The anamorphic skull occupies the lower third of the composition. Holbein has painted it by setting up his picture plane at an extreme oblique angle, drawing the skull in perspective from that angle, and then reorienting the picture so that the skull appears stretched and distorted when viewed straight on.

The optical effect requires the viewer to stand at a specific position to see the skull correctly: approximately a metre to the right of the painting's centreline, with the eye at roughly the level of the painted floor. From that position, the smudge resolves into a skull rendered with the same precision as the rest of the painting.

What the Skull Means

The skull is a memento mori, a reminder of death. The convention was familiar in sixteenth-century European art: still-life paintings included skulls, portraits of scholars often had skulls on the desk, devotional images of saints frequently showed them holding skulls. What is unusual about Holbein's skull is the optical trick.

The trick is the point. The painting argues, in its structure, that knowledge of death is something the viewer has to work for. From the front of the picture, the diplomatic pomp and intellectual achievement of the two sitters are perfectly visible. The skull is hidden in plain sight as a stretched smudge. Only by moving to a specific angle can the viewer see what underlies everything else.

This is a sophisticated theological argument, and it would have been read as such by Holbein's contemporaries. The skull's invisibility from the centre, and its visibility from the side, mirrors a Christian commonplace: that death is always present in life but rarely attended to. The painting requires the viewer to physically perform the act of attention. You have to move to see it.

The Crucifix

In the upper left corner of the painting, partly obscured behind the green curtain, is a small silver crucifix on a chain. It is easy to miss. Holbein placed it there to balance the skull diagonally: the skull at the lower right, the crucifix at the upper left. Together they make the painting's frame: death below, salvation above, the ambassadors and their worldly inventory between.

The compositional balance is exact and was certainly intentional. Holbein worked from carefully prepared cartoons (preparatory drawings at full scale), and the placement of every element in The Ambassadors was decided before any paint was applied.

Holbein at the English Court

Holbein was born in Augsburg in 1497, trained with his father, and worked in Basel before moving permanently to England in 1532. He had visited London briefly in 1526 to 1528, carrying letters of introduction from Erasmus to Thomas More. The 1532 move was permanent because the Swiss religious reformations had reduced demand for the kinds of religious painting he had been doing in Basel.

He arrived in London the year before The Ambassadors and quickly built a portrait practice. By 1535 he was the King's Painter. Over the next eight years, until his death from plague in 1543, Holbein produced the canonical portraits of Henry VIII, the court, the king's wives, and the diplomatic corps. The Ambassadors, painted in his first full year in England, was the commission that established his reputation.

What the Painting Shows Beyond the Trick

The anamorphic skull is the famous thing, but the rest of the painting is doing similar work less spectacularly. Each object on the cabinet is positioned exactly. The astronomical instruments have working settings: a specialist can read the time and date of the painting's depicted moment from the instruments' positions. The lute has been drawn so accurately that musicologists can identify the instrument's maker. The carpet on the upper shelf is a recognisable type of mid-sixteenth-century Anatolian Ottoman weaving.

The two men's clothes are similarly precise. De Dinteville's pink satin lining is a specific dye colour produced in Lyon. His ermine is the winter pelt of a specific marten species. The medallion he wears is the Order of Saint Michael, the highest French chivalric honour, awarded to him in 1531. De Selve's black robe is the cassock of a French bishop; the colour and cut are correct for his rank in 1533.

What Holbein Left

The painting hung at de Dinteville's country house at Polisy in Champagne for the rest of his life. It passed through several French private collections after his death, was bought by the National Gallery in 1890, and has hung there since. The skull continues to require viewers to move sideways to see it.

Holbein produced approximately one hundred and fifty paintings, several thousand drawings, and a substantial body of woodcut and engraving designs in his fifteen-year career. He died in London in October 1543, aged forty-six, during a plague outbreak. He left no major students and no school of followers in England; English painting for the next century looked nothing like Holbein. The kind of painting he could do (the technical precision, the intellectual programme, the formal experiment) had no native heir in England and was not picked up there.

It was picked up elsewhere, slowly. The anamorphic device became fashionable in the seventeenth century, particularly in France and the Low Countries. Vermeer used optical aids of a related kind. The whole question of what a painting can hide in plain sight has Holbein's skull at its origin point.