ART / Dull, mediocre, bad - and well worth the price of a ticket: Mengs is the prototype for the B-list celebrity, famous for being (briefly) famous. Andrew Graham-Dixon reports

ANTON RAPHAEL Mengs was the most famous painter of the 18th century - for about 15 minutes. In 1761 he painted his presumed masterpiece, a large but flaccid canvas, conflating hints adapted from Raphael and Poussin, which he entitled Parnassus and which was, briefly, one of the most highly regarded pictures in the world. On the strength of what now seems a stunningly dull mythology, with its wooden Muses and mannequin-like Apollo, Mengs was acclaimed by the first great arbiter of Neo-classical taste, Johann Joachim Winckelmann, in terms which any artist at any time in history might have had trouble living up to: 'He is the greatest artist of his time and perhaps of succeeding times, reborn like the phoenix from the ashes of the first Raphael, to teach the world beauty in art, and to achieve the greatest flight committed to human powers in the same.' But within a few years Mengs and his works would abruptly disappear into obscurity. Winckelmann's phoenix turned out to be nothing of the kind, but a dodo of the Neo-classical age.

Conclusive evidence comes in the exhibition devoted to Mengs that currently occupies the upper galleries of Kenwood House. This is something of a rarity: a show consecrated to the talents of a hopelessly mediocre painter that is none the less fascinating; an exhibition of irredeemably bad art that also amounts to a study in ephemeral artistic celebrity.

Mengs was not only the victim of Winckelmann's wild over-enthusiasm - although, had Winckelmann not damned him with such strong praise, he might never have attracted the venomous dislike that has characterised most later descriptions of his work and would, probably, have been remembered as a merely competent practitioner of a style of painting that became briefly fashionable in Rome in the third quarter of the 18th century. But it seems that he was doomed from birth to carry a weight of expectation that he could not support.

Mengs' father was an embittered, frustrated minor painter of portraits who lived out most of his life catering to the vanity of the court circle of the Elector of Saxony. Clearly desperate to see his son succeed as he had never done, he condemned him at baptism to a lifetime of hopeless dreams and inappropriate aspirations. Mengs' given names - Anton after Antonio Correggio, and Raphael after the Renaissance prodigy - amounted to an albatross around a baby's neck.

Mengs senior brought up Mengs junior to believe that he was destined for great things. He took him to Rome, introduced him to the great and the good (such as Cardinal Albani, the influential connoisseur and collector for whose private gallery the Parnassus was commissioned) and, for a while at least, the sheer desperation that lay behind his urge to impress carried him through. But in the end his tragedy may have been that he was no more and no less than the son of his father: a moderately talented portrait painter whose almost complete lack of feeling and imagination fatally unsuited him to the genres of mythological or biblical narrative painting which he saw as his route to greatness. His proper domain was the world of fashion-conscious cognoscenti and dilettanti, of English milords dallying with classical culture while on the Grand Tour, of which he left several records in the form of dutiful but uninspired portraits. It was not Mount Parnassus.

The Self-Portrait that Mengs painted in 1774 is a more confessional picture than, perhaps, it was intended to be. Mengs clearly meant it as a document of his supreme self-confidence, an image of himself as Winckelmann's phoenix. The artist, soberly dressed and simply lit against a plain background, gestures to the canvas beside him on which he has traced out some evidently classical figures in flowing draperies. The painting is Mengs' way of spelling out, in no uncertain terms, that he is the new heir to the Renaissance - that in him, as in no other painter of his day, the spirit of classical antiquity still lives. But although Mengs' self-portrait clearly occupies a long-established tradition of pugnaciously self-propagandising artists' paintings of themselves, there is, none the less, something slightly unconvincing about it. The man at the centre of the charade seems conscious, after all, that it is a charade. The expression that he has given himself (and whether this was involuntary or not, the Self-Portrait is by some way the most expressive painting Mengs ever painted) is the giveaway. There is fear, and sadness, in his eyes, the look of a man who knows that one day people will see through him.

In Rome Mengs married the daughter of a dustman, and she is said to have posed for the figure of the Virgin in his The Holy Family with St Elizabeth. This seems unlikely, to judge by the painting itself, one of Mengs' most shameless attempts to follow in the footsteps of Raphael. Nothing remotely as robust as the likeness of a real person has been allowed to intrude into this monument to Mengs' pained academicism, a painting made up entirely of magpie-like borrowings from the work of the High Renaissance master he sought to rival but could only parody. Each of the figures, whether the overly solicitous Virgin or the daftly beatific, ludicrously ill-proportioned infant Christ, looks like the shadow of a shadow of an art historical source, as if ineptly copied from some inept engraving of a Raphael original.

The puzzle of Mengs' sudden and temporary celebrity, to modern eyes, is that it could ever have happened - that anyone, looking at this painting (or the Parnassus which now loiters, dark and unseen, in the Villa Albani in Rome; or the equally inert Augustus and Cleopatra which hangs, universally ignored, at Stourhead), could ever have believed that Mengs was anything other than a painter of the third rank with pretensions. The minor dramatist and amateur art historian Richard Cumberland, writing just three years after Mengs' death, put the seal on his posthumous reputation. 'Mengs,' he wrote, 'was an artist who had seen much, and invented little. He dispenses neither life nor death to his figures, excites no terror, rouses no passions, and risks no flights. By studying to avoid particular defects, he incurs general ones, and paints with tameness and servility in all or most of his compositions, in which a finished delicacy of pencil exhibits the Hand of the Artist but gives no emanations of the Soul of the Master; if it is beauty, it does not warm, if it is sorrow, it excites no pity.'

Yet Cumberland's damnation of Mengs may also account for his momentary apotheosis. Mengs' dull and lifeless paintings clearly answered a need, even if their virtues were entirely negative. The kind of Neo-classicism that Winckelmann espoused in the second half of the 18th century was itself underpinned by a kind of negative aesthetic, an aesthetic in opposition to all that the Rococo style seemed, to him, to embody: decadence, frivolity, the unashamed carnality of Boucher and Fragonard, those painters of airborne brothels. Mengs' academic, by-rote method of painting, the pallidity and bonelessness he imparted to human flesh and his confinement of all human activity to the feeble gesturing of figures half- heartedly enacting morally uplifting narratives from the Bible or classical myth - these were all, to Winckelmann, virtues of the highest order.

Mengs appealed to Winckelmann for exactly the same reasons that the bleached fragments of surviving classical statuary appealed to Winckelmann: they allowed him to indulge his fondness for looking at the nude human body while rendering it harmless by presenting him with the human body unsexed, made marmoreally frigid, taken out of the domain of real life, real (and dangerous) passion. Winckelmann, the first of art history's long line of shamefaced closet homosexuals, was terrified of his own urges and required art to act on his nervous system like a form of sedative, or purgative. 'Beauty,' he wrote, 'should be like the best kind of water, drawn from the spring itself; the less taste it has, the more healthful it is considered.' It was Mengs' good and bad fortune that, through sheer cultural accident, his art happened to fit the devious prescriptions of the most influential writer on aesthetics of his age. He became famous, quite simply, because his art was so thoroughly unengaging, so cold and emotionless, so unrelieved by virtuosity and so without sensual appeal that it met Winckelmann's peculiar needs. He became famous because Winckelmann found in his painting the cold shower that his overheated sensibility required. No wonder that the temporary celebrity of Anton Raphael Mengs, which depended precisely on all his worst qualities as an artist, did not last.

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(Photograph omitted)