The subjects of Lucian Freud's early drawings and paintings are so there it hurts. Enormous eyes stare painfully, heads framed in hair bristling as if electrified. Animals quiver with presence. A parrot fixes us with triangular black pupils, and even an ex-chicken, head in a bucket, pierces the air with claws as defiant as a revolutionary's raised fist. An aloe plant points a jagged, broken leaf like a weapon, the effect doubled by an ominous shadow. These pictures are much smaller than more recent and famous Freuds, some not even A4 size, but their fierceness is triple distilled.
The birds and women reflect, like polished metal, the way Freud looked at them, a ravenous glare that took in every detail with the intensity of the Pre-Raphaelite, the Surrealist or the mad. The women look more than mad themselves. One of them regards us with the blankness of the shell-shocked from behind a table where a lone tulip, its stem snapped just an inch or two below the blossom, lies like collateral damage. The neckline of another's white pullover, asymmetrical beneath a dark jacket, cradles her neck like a hook.
In some of these works, the "coiled vigilance", in Lawrence Gowing's phrase, of Freud's gaze lashes out at reality, squashing and twisting faces. Some challenge us not to look at what we would usually avoid, with subjects such as the chicken or palettes of unremitting ugliness. Village Boys of 1942 (Freud is peeping over the back of a chair) is almost entirely painted in the two most repulsive colours in existence: maroon and teal. Yet the collage-like organisation of the picture, the tension between caution and confrontation (another boy, larger, faces us with double-barrelled eyes) are as riveting as they are unnerving.
Where did these paintings come from? There was a Jewish boy's childhood in Germany, ended by his family's flight to England in 1933, when Freud was 11, to instil watchfulness, strength, detachment. There were Freud's masters and friends: a prodigy, he was surrounded by admirers from his schooldays. The no-rose-without-thorns spikiness could have been lifted from Graham Sutherland. The huge eyes and hammered-flat faces were definitely taken from Cedric Morris, a much-undervalued artist, who, Freud said, taught him how to paint.
The question of what is being served by Freud's intensity is, however, harder to answer. The eyes in these youthful pictures are shields rather than windows, symbols rather than explanations. In the large portrait of Henrietta Moraes, then his mistress, Freud attempts something softer: bare-breasted, wrapped in a blue blanket, she poses before a window, the chill of early-morning light and a leafless branch counterpointed by the yellowish green tinting the hair at the top of her head the colour of burgeoning spring. Yet, despite the care Freud has lavished on this pagan madonna, she remains a poetic abstraction.
The later paintings here show Freud arriving at the style by which he has been known for the past five decades. A man in a 1957 portrait appears almost flayed, his grey-green muscles contrasting with burnt sienna flesh, an unhealthy green aura radiating round his ears. Unlike the heavy applications of paint that Freud used in the following decades, the pigment is thinly applied, scraped back, and in places, incised. It remained only for Freud to slap on the impasto, the putty-like colours and leaden, granulating Cremnitz white that have served him for sickly flesh and that are a testament to his struggle and anguish.
One can see why Freud discarded the style and scale of these fierce little pictures: the times and his ambition demanded bigger canvases, wilder emotion, more paint. But, as with his fellow artist in unease, Harold Pinter, the later works often have little to sustain them but anger and a desire to dominate. This show is made up of souvenirs from a time when Freud was saying, "Look at this," not "Look at me."
To 12 December (020-7839 7600)