Lucian Freud: Portraits, National Portrait Gallery, review: A show that proves Freud's greatness Formalist critics dislike this biographical approach to looking at art, but with artists like Picasso and Freud it is inevitable because the success of their portraits usually depended on the emotional, psychological or erotic connection they made with their sitters. In the case of Freud, this diaristic reading of his portraits had begun to happen long before his death. Despite deadpan titles like Girl in Bed and Girl in a Green Dress, it is generally known that a series of crystalline early portraits show his radiantly beautiful second wife Caroline Blackwood, while the disintegration of their marriage is chronicled in a double portrait of the painter and his wife in a Paris hotel room at the very moment when each in their own way understands that whatever has just been said between them is irreparable. Freud perfectly captures the abject misery of lovers who recognise the emotional chasm between them. In his later work, Freud would often try to suppress his own feelings to focus on those of his sitters. In his staggeringly beautiful Man in Chair, he succeeds in doing what very few artists have ever done - to somehow suggest the many layers of contradictory experiences and impulses that go into the make-up of a flawed, human, and highly complex man. The label tells you the sitter was Baron Heinrich von Thyssen, and you instantly sense that this man is racked with anxiety. Gradually you grasp that the source of his confusion is nothing more worrying than the experience of sitting for his portrait. All of the picture's visual tension is located in the prominent veins of the hands and the long, tapering fingers he is pressing so hard into his thighs. The gilded armchair, upholstered in red velvet, that he clearly brought with him to the studio speaks of the insecurity of a rich man who is ill at ease outside his accustomed milieu. And only the most uptight of sitters would feel the need to wear a buttoned-up business suit with a white shirt and tie when sitting to Freud. And by the way, the artist responds to the Baron's obvious distaste for his grubby surroundings by adding an entirely unnecessary (but deliciously painted) pile of paint-stained rags behind the chair. He wants no one to mistake the setting for one of Thyssen's many homes - or to make the error of imagining that he, Freud, came to the Baron's place to paint his portrait, and not the other way around. It's when Freud allows us to see human frailties like this that he is at his best. A gangster whose face has been hideously slashed by razor blades looks out of the picture at us - but hesitantly, as though used to the reaction of people who avert their eyes when they see his scars. The look of pain in his eyes is replicated in the face of the daughter he draws close, and to whom he has passed down not only his build and facial features, but also a burden of sadness that is heart-breaking to see in one so young. As a general rule, the simpler Freud kept his compositions, the more successful the outcome. Nothing detracts from the intensity of his studies of the head of the tormented artist John Minton or the small 1972 study of his still-fierce mother. In the nearly monochromatic portrait of the Duke of Devonshire, simply by scumbling purple into the light-grey background Freud envelopes the sitter in air and light. Until I read Martin Gayford's riveting account of sitting for his portrait, I had not understood how Freud uses accents of strong colour like the electric-blue scarf as tonal devices to make the varied colours in the face register as monochromatic. In some cases, Freud will build a sitter's character on a detail of clothing - the long red stripe on the trousers of Andrew Parker-Bowles's uniform is one example; another is the pink nail polish and butterfly-patterned jersey worn by an elderly woman whose strong face and red-rimmed eyes suggest anything but a frivolous interest in feminine or coquettish things. But all painters have to set themselves new challenges, and that's what Freud did in later large-scale figure compositions such as Large Interior W11 (After Watteau), or the pictures in which the naked models assume grossly contorted poses or are placed in irrational juxtapositions with other figures. These - a red-haired man crouching on a chair or a naked youth clutching a rat - are far less compelling for me than the straightforward character studies. And in the last galleries, the acres of flesh on view sometimes felt more like still lifes than portraits, though they certainly show how Freud carefully distinguishes between the flesh colour of a young woman, the blotchy pallor of an Irishman's torso and the unhealthy grey skin of a dying man. I don't mean to carp. This is by far the best large selection of Freud's work I've seen, and in addition to some of the paintings we all know like the backs of our hands, there were plenty of pictures I hadn't seen before. After a celebrated artist's death, his reputation often dips. On the basis of this one exhibition I predict that the opposite may happen with Freud. No longer in need of the great man's approbation, curators will explore aspects of his life and art that were off limits before. From Thurs until May 27