Diego Rodríguez de Silva y Velázquez was "the painter of the painters", declared Édouard Manet - but he was much more than that. The days when artists played a leading role in national or international politics are long gone (what does this say about the cliquey introspection of today's art world?), but while Velázquez's work is justly celebrated for its aesthetic achievements, far less well known is the role he played in articulating the political imperatives of his masters.
The work has become divorced from its poli tical context largely because it is so seductive as art. The breathtaking ease of the brushwork, the huge but seemingly effortless restraint with which Velázquez controlled his colour palette and pictorial composition, the sheer facility of draughtsmanship: all are amply demonstrated at a forthcoming exhibition at the National Gallery in London - amazingly, the first ever monograph show in the UK of Velázquez's work.
The palace of San Lorenzo de El Escorial towers 400 metres above Madrid, the highest cap-ital city in Europe. Designed by Juan Bautista de Toledo, a pupil of Michelangelo, it encompasses a monastery, two churches, a sacristy, the mausoleum of the Spanish kings and more besides. It was in these dark corridors that Velázquez performed that most delicate of tasks for an artist: the creation of images that squared dynastic continuity with religious piety. His duties were several: as portrait painter from 1623 to King Philip IV, Velázquez did not just create likenesses of the king (who, exceptionally, granted the artist at least five separate sittings over the course of his life). He was also charged with ensuring that all other portraits of the king, many of which were sent abroad as essential props of diplomatic theatre, conformed to strict etiquette. He was, in effect, guardian of the king's image.
At El Escorial, there was no division between church and state. The grey granite surface of the enormous building is abrasive, laboriously constructed and immutable; visitors passing beneath the four-metre-high statue of Saint Lawrence that stands above the central door on the front façade quickly sense the intensely focused atmosphere inside the palace walls. Courtyards lead past library windows and princely apartments to the source of ultimate wisdom, the mighty basilica.
Precedent for Velázquez's intriguing political function was set by the artist Francisco Pacheco, head censor of the dreaded Inquisition in Seville, who also happened to be Velázquez's father- in-law and teacher. Pacheco had the ear and admiration of Caspar de Guzmán, Count-Duke of Olivares, a black-bearded and black-robed manipulator who was chief minister to Philip IV. His sinister and powerfully controlling influence is evident in both the Velázquez standing portrait of him and in the softer, but still politically charged painting of Philip IV's boy heir Baltasar Carlos testing his small horse outside the royal mews. Olivares was clearly monitoring the welfare of Spain's most precious possession. (In fact, the prince died before reaching puberty.)
Velázquez was also given the task of managing the collection of works of art within El Escorial. In an age when paintings and their display conveyed a range of overt and subtle meanings to Spanish and foreign visitors alike, this was no humdrum responsibility. Even today, British ministers' choice of art for their offices and apartments is subject to agonised wrangling by civil servants as to which political messages could be construed from them.
Visitors to El Escorial today get to see only a fraction of the curatorial hang arranged by Velázquez. But in the chapter house you can still get a sense of his artistic and editorial values. On the ceiling is a field of gently elegant grotesques, all mermaids' tails and goat masks. Its frivolity is surprising amid the sobriety of this ashen-faced palace. Commissioned by the painter himself and executed by artists specially imported from Geno a, it shouts high fashion. Raphael had set the standard for such decoration with his Stanze for the Vatican, home to Spain's greatest rival Catholic power.
The heart of Velázquez's curatorial plan lies on the wall above the altar: Titian's painting of Saint Jerome, showing the 4th-and 5th-century father of the church praying in what was supposed to be the wilderness of a Syrian desert. This signals the high favour that the Venetian 16th-century artist had in royal circles. Titian had been the favourite painter of Philip IV's ancestor Charles V; as Holy Roman Emperor, Charles is said to have picked up Titian's fallen brush when visiting his studio.
But the respect that Velázquez had for Titian was more personal. Here was an artist whose astonishing range of styles was unparalleled. Placing his painting above the high altar was as much a homage from one artist to another as an auspicious piece of religious propaganda. It was this demonstrably critical understanding that won Velázquez the prestigious wardenship of El Escorial in 1652, a role that guaranteed his control over the care of the palace complex.
Politics is all about access, and what better evidence of Velázquez's access to the very centre of power - the king and his family - than his 1656 painting Las Meninas (see Richard Cork, previous page)? The image was intended to be hung in the private royal apartments and not for general public display. As such, it is an essay in intimacy; this is as close as it gets. The interior scene represented in the painting also shows something of the way works of art were hung: it is thought that all the pictures shown on the background wall are of mythological subjects. Although the king was the champion of true Christendom in public, an altogether more varied persona revealed itself in his domestic family life.
And yet, ultimately, all the control over the king's image could not change the fact that Spain was in retreat. The country lost Portugal in 1640, the Netherlands in 1648 and the frontier fortresses of Flanders in 1659. Spain's diminishing political strength is piteously mirrored in the deaths of the two male Habsburg heirs painted by Velázquez. In retrospect, it seems only appropriate that the artist's other duty was to direct the decoration of the family's mausoleum, a chill gold-and-liver-coloured hexagonal chamber located deep in the palace. Two empty sarcophagi still await the remains of the parents of the present Spanish king, Juan Carlos I.
Velázquez's work is now free from politics and the concerns of power; all we are left with is the art. That it still has such independent strength is a testament to his supreme gifts.
"Velázquez" opens at the National Gallery, London WC2 on 18 October and runs until 21 January 2007. www.nationalgallery.org.uk
Sadly, Velázquez's most admired painting will not be travelling from Madrid for the National Gallery's much-awaited exhibition. Las Meninas is far too much of a revered national treasure ever to leave its place of honour at the Prado. But its absence from London need not prevent us from asking: What makes this canvas such an outstanding example of his work?
When Velázquez painted Las Meninas in 1656, he must have hoped that it would come to be regarded as his masterpiece. This mesmerising canvas is his most personal, revealing a great deal about his own ambitions at the Spanish court. And it has become mysterious, igniting endless debate about the artist's intentions.
No doubts surround the identity of the figures assembled here. At the centre stands the little infanta Margarita Teresa, daughter of King Philip IV and his wife Mariana of Austria. Their two faces emerge, hauntingly, from the dark mirror hung at the far end of this lofty, imposing room. But our attention is dominated by the courtiers in the foreground and, above all, by the maids of honour (las meninas). One, María Agustina Sarmiento, almost kneels in homage as she offers the little princess a red beaker of water. The other, Isabel de Velasco, hovers protectively above the girl. And in the right corner are two dwarfs, Maribárbola and Nicolasito Pertusato, who places a presumptuous foot on the king's favourite dog.
Together with the chaperones behind and the chamberlain Don José Nieto, silhouetted in the distant doorway, these figures give us a vivid, immediate sense of life at the royal palace in Madrid. The painter lets the sun from the open window invade their forms, giving them an astonishingly persuasive presence. We feel almost capable of reaching out to touch them, beguiled above all by Velázquez's ability to make their flesh, hair and clothes sparkle with luminosity.
Gradually, however, we grow aware of Velázquez himself. There he is, standing on the left with brush and palette, poised to make marks on a colossal canvas. But who is he painting, and why is he looking out in our direction? The infanta also seems to be gazing at us, as do one of the maids of honour and the chubby female dwarf. Suddenly, almost with a shock, we realise that they might all be looking at Philip and his wife, who are probably standing in the space we ourselves occupy in front of this hypnotic picture.
So the Spanish king and queen are posing for their portrait or visiting Velázquez's studio to watch their infanta being painted. Either way, that would explain why the blonde-haired girl seems to be on display, trying her best to adopt a suitably regal pose. Velázquez ensures that she is by far the most light-suffused figure in the painting. And a later addition to the painting makes him look proud: the cross of the Order of Santiago on his doublet - an honour marking the respect he enjoyed at the royal court. He fought to attain this position for many years, at a time when artists normally settled for a much less exalted position in society. Thus, his ability to portray himself here is, on one level, a celebration of his worldly success.
And yet, on another level, one can detect an air of melancholy in the artist's grave face. Both he and the royal couple reflected in the mirror beyond look ghostly in comparison to the infanta, with her dazzling, precocious poise. It is almost as if Velázquez is meditating here on his own mortality: he died only four years after completing this brilliant, profound and, above all, inexhaustible painting.
Richard Cork presents "The Painter's Painter: the dazzling Diego Velázquez", on 29 October at 9.45pm, BBC Radio 3