The longer Lucian Freud lives, the more defiant he becomes. Spurning the convention of displaying his new work in a bare white gallery, the 81-year-old artist has opted instead for the Wallace Collection. In his honour, an entire gallery was cleared of Dutch old master paintings. And Freud did not insist that his show should conform to fashionable ideas about minimal hanging. Far from giving each picture an immense amount of space, he has allowed them all to be placed cheek by jowl. No fewer than four etchings and 18 paintings have been crammed into a modest-sized room. They bombard us with their combined visual impact, more redolent of a crowded collection from the past than a cool, contemporary show.
Freud's subjects can be freighted with history, too, and none is more so than The Brigadier, a towering full-length portrait of Andrew Parker Bowles. Arrayed in full military uniform, the ageing lothario (who was once married to Camilla) leans back in an armchair and crosses his long legs with an air of nonchalance. The pose enabled Freud to flaunt the bold red stripe running down the brigadier's trousers. And the glinting medals on his jacket are proudly lined up for inspection as well.
So far, the painting reminds us of country-house portraiture at its grandest. But Freud, as an artist, is far removed from Reynolds, Lawrence, Tissot and Sargent. He has subverted all this seeming formality by allowing us to detect that the chair is just a well- worn studio prop, with a sheet covering the faded seat. Instead of buttoning up the brigadier from his waist to his stiff gilt collar, Freud let the jacket burst open, revealing an ordinary white shirt bulging with a substantial paunch. The brigadier's left hand, splayed on the arm of the chair, turns out to be surprisingly small, with delicate, bony fingers. But fleshiness reasserts itself in Parker Bowles's face. Flushed and puffy, he seems the victim of too many port-fuelled military dinners. And his downcast eyes, with their drooping lids, have a look of disappointment. He appears melancholy, lost in a gloom that is deepened by the darkness of the screen behind him.
We are a long way, here, from the robust, complacent arrogance of the imperial officer class. We would not be astonished to find Parker Bowles naked in another painting. And certainly the Wallace show, focusing on the large and impressive body of work Freud has produced since his Tate retrospective in 2002, contains several outstanding nudes.
Some of these paintings are of his studio assistant, David Dawson, whose recent photographs of the artist and his studio now make a compelling exhibition at the National Portrait Gallery. Freud can move at will from large to more intimate-sized canvases. One of his small paintings shows a naked Dawson reclining with two dogs, Eli and Pluto, for company. The dogs are dozing, and lean against the man's hefty bulk as if for comfort. But Dawson remains alert, with one hand propped against his head and the other resting on Pluto's body. The gesture looks protective, and turned out to be sadly prophetic because Pluto, who appeared in many earlier canvases, died last year. Freud has commemorated her simple garden grave in another small painting, where autumn leaves add to the elegiac mood.
Eli survives, and makes a second appearance with Dawson in the most startling, ambitious exhibit. This time, the naked man is displayed in a far more brazen attitude. Seen from above, he lies on his back across a narrow, iron-framed bed. Always a master of painting flesh, Freud has defined the pallor of his model's long, sinewy body with consummate aplomb. But there is plenty of tension here, too. Dawson's left leg juts out sideways before thrusting in to press against his right thigh and calf. The pose discloses his genitals in the frankest manner, yet there is no hint of virile boastfulness. Instead, Freud has emphasised the vulnerability of the nude man, whose right foot dangles loosely over the side of the bed. Beside him, Eli hangs upside down and forlorn. The unease is heightened by the floorboards, which rush up the picture surface with such force that they generate a feeling of instability. And Freud has accentuated the mood by allowing a large plant to erupt beside Dawson, its spiky leaves lancing outwards as if to pierce his left arm.
By no means all the images in this show are disconcerting. One of the etchings, which is also included in the Scottish National Gallery of Modern Art's excellent survey of Freud's graphics, is a tribute to Constable's painting of a sturdy elm. It reminds us that Freud recently selected the works for a major Constable retrospective in Paris. Al-though few landscapes can be found in Freud's oeuvre, he has developed a fascination with the view outside the French windows of his west London home. For example, a canvas called Painter's Garden is alive with sunlight, dense foliage and a sense of the dark earth beneath. Yet it is none the less an urban scene. Freud has never been a painter of full-blown rural subjects. Born in Berlin, he has lived most of his adult life in London. And most of his paintings return, with obsessive regularity, to an encounter with a sitter isolated in a bare room.
Some of them turn out to be his grandchildren. They are quite unlike the brooding, history-drenched effigy of the brigadier. One small boy, the mischievous Albie, sticks out his tongue. And a head-and-shoulders portrait of Frances Costelloe has the immediacy of a snapshot. Although thickly handled in places, it still looks fresh and informal. The fair-haired girl looks down, as if overcome with shyness in the presence of her grandfather at the easel. He first painted her several years ago, as a child with a toy balanced on her head. But this painting is much more sober, and Alice appears absorbed in her own private thoughts.
Even when lying naked on a bed, Freud's adult models look similarly lost in day-dreams. The woman in Naked Solicitor, who has no qualms about sprawling on a sheet with arms behind her head and legs apart, seems oblivious to the viewer. Unlike so many nudes in European art, from Titian to Manet, she refuses to solicit the viewer's gaze.
The naked woman in Portrait on a White Cover is even less concerned about her surroundings. Resting her head and left arm on a pillow, she succumbs to sleep. As though in response to her placidity, Freud devoted a large expanse of this image to the smooth fabric spread across the bed. Its serenity contrasts with the restless folds of the sheet in Naked Solicitor, and even more with the disturbance rippling through the bed linen in a small painting called After Breakfast. The nude here looks strangely hunched and exhausted, while the creases in her sheet intensify the sense of unease by evoking the turbulence of a stormy sea.
Like his grandfather Sigmund, Lucian Freud has always thrived on unearthing disquiet. And in his superb etching Girl with Fuzzy Hair, the curling tendrils explode with such force that they seem to reveal the full extent of the psychic tension within her sombre, meditative face.
"Lucian Freud: latest paintings" is at the Wallace Collection, London W1 (020 7563 9500) until 18 April; "Lucian Freud in the Studio: photographs by David Dawson" is at the National Portrait Gallery, London WC2 (020 7306 0055) until 1 August; "Lucian Freud: etchings 1946-2004" is at the Scottish National Gallery of Modern Art, Edinburgh EH4 (0131 624 6200) until 13 June