Master of mystery, art and invention

Da Vinci's portrait of Cecilia Gallerani is a vision of lithe animation pinned down. Photo / AP

Leonardo da Vinci: Painter at the Court of Milan, the National Gallery's once-in-a-lifetime show, is a revelation from first to last. It contains more than half of all the surviving paintings, so fragile and rare, begged and borrowed from around the world.

These are sparely presented, one or two to a room, the lighting superbly matched to that of the pictures with their pale figures looming out of the dark like night creatures, held fast in knife-edge contours and sealed off by an almost alien perfection. The show is dazzling, mysterious and disturbing.

That there are any paintings to show at all is something of a miracle. Leonardo's career is a catalogue of lost works and false starts. He ruined his greatest paintings, The Last Supper and The Battle of Anghiari, by experimenting with new fresco techniques that entirely destroyed the latter during his lifetime.

His fabled Medusa disappeared long ago and his dream of the world's largest equestrian statue, of Ludovico Sforza, Duke of Milan, never got any further than the clay model later shot to smithereens by French troops.

Leonardo probably started no more than 20 paintings in his 50-year career. Of these only 15 are agreed to be entirely by him so it is remarkable to have nine in this show. He was notoriously slow, reworking a painting for decades, constantly distracted by the visionary machines and weapons, the metaphysical and mathematical speculations, anatomical inquiries and treatises on art for which he is celebrated.

Leonardo is a visual thinker who painted part-time; his mind is only intermittently expressed in paintings as opposed to schemes, sketches and words. So the inclusion of more than 50 of his stupendous drawings - thought-into-line - is apposite.

The show starts with one of the greatest drawings: his vision of how the mind works. A man's head is bisected in profile. The cross-section shows his external appearance - but also his inner being, consisting of three interlinked chambers in the brain. Knowledge comes in through the eye, is processed in the first chamber, understood in the second (the soul) and stored by memory in the third.

Centuries before anyone discovered how the eye works (still less the mind) Leonardo correctly conceives of it as an extruded part of the brain. And when you look from this astonishing image, all its insights condensed in a little page, to the portrait of a musician, borrowed from Milan, this guess becomes true metaphor. The musician's eyes are painted as glinting spheres, all vitality and inner perception. Da Vinci senses the connection between mind and eye: to see is to know.

The Musician is a peculiar painting, with its wooden hand holding a stiff little score. Perhaps these elements are not by Leonardo? Doubts about who painted what keep surfacing throughout the show, but there is no mistaking the young man's angelic nose and lips, or those clouds of curling tendrils that prefigure Leonardo's later obsession with the movements of air and water.

Leonardo is master of the metal point and sharpened quill, transmitting information to perfection on paper, the line controlled, incised, repeated: nothing spontaneous, everything studied. And the empirical character of the drawings - what does the world look like, how do things work - leaves its trace in the paintings.

Look at Cecilia Gallerani, Sforza's 16-year-old mistress, turning towards something or someone unseen. This is a vision of lithe animation pinned down. Her elegant contours are measured by headband, veil, straps and beads, but the painting keeps her tautly confined in its lines. The ermine she holds is Sforza's emblem.

The experience at the National Gallery is of persuasive clarity and intense control, a way of painting disciplined by analysis, vision and pure draughtsmanship. But there is always something else too, something going on that one cannot reach or deduce: what was happening within that second chamber of the artist's head.

* Leonardo da Vinci: Painter at the Court of Milan, at the National Gallery, London, to February 5.