ART / Every picture tells a life story: What makes a good portrait? As the NPG's show of 'Master Drawings' displays, the best likeness is not always the most revealing

MANY WRITERS who are biographers by nature - I wish there were more of us, and fewer novelists - love the National Portrait Gallery, and I was eager to see the show 'Master Drawings', taken from the gallery's permanent collection. The exhibition has had a successful tour of Canada and America, and that's nice, but it doesn't look so hot in London. Many of the drawings that were sent abroad are not on display here and the residue is shown in a basement that doesn't make a proper gallery for thoughtful and understated works, which is what good portrait drawings tend to be.

Still, I liked the exhibition. Here are the likenesses of so many admirable or intriguing people, and the artists who portray them also tell us a lot of little things about the intimate history of portraiture. Government, royalty and nobility are hardly represented. The pictures are characteristically of writers, with poets taking precedence over novelists, and the most moving of them come from the time when poets and artists were closest, the mid-19th century.

Some acts of homage from artist to writer are so vivid that it scarcely matters if the quality of drawing isn't high. That's the case with the two pages taken from Benjamin Robert Haydon's diary. One shows Keats. On the other Keats has drawn Haydon and then Haydon has tried to do his self-portrait, not very successfully. He was a limited artist, and his big ambitions were misplaced. Keats's ambition is seldom discussed, but it was enormous for a cockney lad. Haydon saw this and manages to convey it. He treats the living Keats as classical statuary; appropriately, for if he had lived, Keats might have dropped his Romanticism to become a great Neo-Classical poet.

It may be relevant that Keats's head is not only marmoreal but is seen in profile. Portrait draughtsmen of the Romantic period often went in for profiles, a tendency I associate with the contemporary liking for silhouettes. This was poor people's portraiture, and silhouettes were never made by distinguished or successful artists. Robert Hancock might well have practised this minor skill: certainly he did related work, such as painting heads on porcelain. He would be completely unknown today had he not done this little set of profiles of Coleridge, Wordsworth, Southey and Lamb in 1796-8, just as they were publishing their first books. Technically, they are not very good drawings. But Hancock captured the poets' characters as well as their likenesses, so here's a fortuitous conjunction of an obscure provincial artist with a group of, at that time, obscure and provincial scribblers.

Silhouettes as a small keepsake of a person's looks were killed off by photography. Another form terminated by the camera was the miniature. A number are in the exhibition. Their brilliant and enamelled appearance is because they are often painted on ivory. It's impossible not to admire miniatures, just for skill and craftsmanship, and what a delight it is that they always make men look fancy and effeminate, an effect I don't suppose males would tolerate on a broader scale. My favourite is Richard Cosway's George IV when Prince of Wales. He appears to be in drag but apparently this is the uniform of the Star of the Garter.

Meticulous, intimate painting of loved ones is characteristic of miniatures and in a way was picked up by the Pre-Raphaelites. Their techniques of painting into white were partly derived from the practice of using ivory as a support, and pictures by the virtuosos of the movement, especially Millais, are often like enlarged miniatures. I like William Holman Hunt's chalk drawing of Millais but it's not as accomplished as Millais's picture of Hunt. Note that both these drawings tend toward the oval, the classic format of the miniature.

So does the thoroughly bad drawing of Dickens by the academician Samuel Laurence. It is of 1838, the time of Dickens' first fame, and is the epitome of early-Victorian vulgarity. How curious it is that the most popular man in England was never drawn or painted with the affection people felt for his books and that the icon of his popularity is Luke Fildes's famous The Empty Chair, painted on the day of the writer's death, in which of course Dickens does not appear. Also curious is the general lack of good portraits of novelists in the 19th century. It adds to my feeling that there is something inimical between art and fiction. Can anyone name a novel that convincingly portrays an artist?

Novelists always caricature artists. Anyway, visual caricature is a theme of the NPG exhibition and is represented by, notably, Carlo Pellegrini ('Ape'), the 18th-century draughtsman John Nixon and, perhaps surprisingly, Landseer. Lucian Freud's grotesque view of Lord Goodman is indebted to the caricatural tradition. So are two drawings by Daniel Maclise, an insensitive artist in oil but sharp and dashing in his illustrations of the men of the 1830s who were featured, and often ridiculed, in Fraser's Magazine.

Fraser's was a journal in which reckless high spirits within the staff were fuelled by nightly editorial carousing. One of their happy carols goes as follows:

Merry were the men of Fraser's song,

As they the bottle pushed along:

Surely, thought we, a pleasant thing

It is to hear such minstrels sing . . .

Not as good as Keats, but let's not be fussy. The point is that Maclise's drawing of the Fraser's journalist William Maginn, dazed by hangover, perfectly captures the crazy humour of the paper. Maginn is posed as a gentleman, but then Maclise lets you know that really he's an extremely clever young Irish wastrel.

Touching though many of the drawings at the NPG are, none has the note of tragedy or human drama. Portrait-drawing avoids the histrionic and has no narrative intent. But presentiment of death is not unusual. Impossible to consider Dante Gabriel Rossetti's double portrait of his sister and mother without thinking of mortality. The drawing's mood is grave, weird too. Rossetti couldn't draw women without sensuality but of course his feelings for these particular women would have been chaste. So they are like nuns, but of a spooky order. All is explained by the fact that the artist was himself near to death.

Of modern portrait drawings I appreciate Gwen Raverat on the subject of Keynes, Charles Ginner's self-portrait and Wyndham Lewis's intense presentation of Rebecca West. But on the whole, the quality goes down in the 20th century. Some sheets have no place in a show called 'Master Drawings', like that by Henry Moore. The fact is that Moore couldn't draw at all.

'Master Drawings': National Portrait Gallery, WC2 (071-306 0055) to 23 Oct.