ART / Faces of history: Andrew Graham-Dixon on David's Portrait of the Vicomtesse Vilain XIIII and Her Daughter, 'a masterpiece of frank and unaffected tenderness'

Shortly before losing the battle of Waterloo, Napoleon visited the painter Jacques-Louis David in his studio. He arrived in a dark mood which was not lightened by contemplation of the vast canvas to which David had devoted 14 years of his considerable but intermittent energy, Leonidas at Thermopylae. Napoleon had never liked the painting because he considered its subject, the stoical acceptance of a military defeat, an unlucky one. But he produced an elegant compliment none the less: 'Continue, David, to illustrate France with your works. I hope that copies of this picture will soon be hung in military academies; it will remind cadets of the virtues of their calling.' The two men parted amicably, and never met again.

Shortly afterwards, David linked his own fate inextricably with that of Napoleon by subscribing to the acte additionnel, which denied the right of the Bourbon monarchy to rule France. Following Napoleon's defeat and the Bourbon restoration, David was made to feel the full force of the new and precarious regime's displeasure. All those who had supported the acte additionnel, it was announced, 'are exiled in perpetuity from the kingdom which they must leave within one month, under penalty of Article 32 of the penal code.' He left Paris at once and chose to spend the remainder of his life in the uneventful obscurity of Brussels.

Once the most celebrated painter of France's most turbulent years, once the intimate of Robespierre, once the pageant- master of the Revolution and creator of the cults of its martyrs Marat and Lepelletier, once the propagandist of the First Empire and the unrivalled chef d'ecole of French Neo-Classicism, David would occupy much of his last eight years in painting bourgeois Belgians. Having spent the previous four decades of his life at the epicentre of history he found himself suddenly consigned to its margins, living in a town whose most conspicuous feature, he noted, was the spotlessness of its streets. Brussels was David's St Helena.

The National Gallery recently acquired a great painting by David which sheds new light on this little studied, little regarded period of the artist's life. It is a work which, previously almost unknown, may help to revise the standard but ill- considered art historical view that his last years were marked by decline and melancholy, a dispirited and uninspired moping towards death. Purchased for pounds 3.5m, by no means an exorbitant price given the extreme scarcity of pictures by David still in private hands, it is a remarkable addition to the national collections of art.

David's Portrait of the Vicomtesse Vilain XIIII and Her Daughter is a masterpiece of frank and unaffected tenderness that may, too, have subterranean depths of meaning. It is one of the least strident pictures that David ever painted, this picture of a young woman and her five-year-old daughter posed, but not too formally, in a plain well-lit interior. The painter is almost exclusively absorbed by the substantial presence of his two sitters, whom he has portrayed in a style which seems more Flemish or Dutch than French. These are not the hard marmoreal beings of David's Neo-Classicism, but warmer and more palpable creatures, flushed and vital.

No attempts have been made to idealise, the style of the painting implies, to smoothe out the protuberance of a nose or improve the contour of a cheek. The mother sits patiently, gazing mistily into the distance of her own thoughts. The little girl is curiouser and more self-conscious. She wonders what the painter is doing, behind his easel, and concentrates on holding her smile in place.

The Vicomtesse Vilain XIIII, who was, like David, a Bonapartist exile from France, seems to have found the process of having her portrait painted singularly dull. Her letters, recently discovered in a Belgian archive, testify to the tiringly methodical thoroughness with which the artist set about her likeness. 'I am beginning to think that my portrait will be quite good, but I admit that the whole thing is extremely boring. The day before yesterday the sitting lasted from 11 to 3.30, and was for the forehead and eyes; yesterday's sitting lasted from 11 to 2.45 for the nose and cheeks. Today he will do the chin and the mouth.' How straightforward she makes it sound. Having decided on his composition and roughed it on to the canvas, David proceeded, part by part, to assemble his images of mother and daughter. Yet the finished painting is nothing like the laborious inventory of detail suggested by the method. Two different human beings - David has painted them in different focus, the mother slightly sharper and more statuesque, her child softer and more potentially mobile - have been granted that form of perpetual life which is a great portrait.

The picture seems charged not merely with life but with a significance that goes beyond a painter's record of what two particular people looked like on a certain week in May 1816. David's portrait is too assertive in its realism to be read as an allegory, but it does have a muted allegorical dimension, which is to be found in the emphatic contrast between mother and daughter. This is a picture of innocence and experience, youth and an older and wiser condition of life that seems tinged with melancholy; and a picture of the bonds of affection that join the two. It is a picture of nurture, whose most affecting detail and most subtle invention is the twined arms and softly touching fingers of mother and child. The child draws her mother's arm and fluid orange shawl around her. Comfort is unthinkingly sought and instinctively given.

Few painters have been as hardily adaptable as David and to see this portrait is to see him, late in life and in unpromising circumstances, devising an entirely new style and perhaps an entirely new moral base for his painting. Just a year after his last appearance on the world stage, that curious and emotional meeting with Napoleon, we find him creating a quite new sort of art for himself. Its style may be appropriate to exile since it is a style of renunciation, implying valediction to one world and embrace of another.

The background to the painting is part of its meaning and may partly explain the almost unsettling intensity of its realism, the sense of an artist releasing himself into the everyday world of people and things. It is the work of a painter who has spent almost his entire life in the service of one or other political cause or ideal and the world of his painting has been, overwhelmingly, an idealised martial and masculine world: a world of heroic action, of dangerous moral enthusiasms, of Revolutionary zeal or imperial hubris. But here we see David turning his back on all that and sympathising, simply but profoundly, with a mother and her daughter.

There had been other moments of moral or political disillusionment when David had rediscovered his humanity by painting portraits, but perhaps none when he had felt so terminally disenchanted as this. He had lived through the Terror and through Napoleon's long years of blood and he was tired. These two still people may, perhaps, stand in for the silent victims of all the bloody heroics of French history that David had seen. They may be David's archetypes of the people who, generally unnoticed, are left to count the cost of men's aggression. All women and children may be implied in this picture of one woman and her child.

David's didactic pictures are full of busy, gesticulating hands and arms and when they have, occasionally, been stilled, their stillness is portentous and heroic, like that of Marat's limp arm in perhaps his most famous painting of all. Now, however, David has found another kind of stillness, the stillness of affection. Having spent his entire life attempting to define and picture the nature of human heroism, he finds it staring him in the face in a room in Brussels. The discovery has the air of a revelation. His picture celebrates, not an active or impulsive form of heroism, but one that is slow and instinctive: not the sudden heroics of action, but the calm and persistent heroics of love.

(Photograph omitted)