Leonardo da Vinci: The flights of the mind by Charles Nicholl

Any biographer of Leonardo must solve a number of puzzles. Charles Darwent attempts to break the code

There's a moment early on in Charles Nicholl's new biography of Leonardo where you find yourself catching your breath. Nicholl is writing about the artist's birth, recorded in a notebook by his grandfather, Antonio: "There was born to me a grandson, the son of Ser Piero my son, on the 15th day of April, a Saturday, at the 3rd hour of the night." Nicholl then works out, in that Nicholly way of his, the likely date of the baby's baptism - "Sunday 16 April, which in 1452 was the first Sunday after Easter, the domenica in albis" - nods to Emil Möller, the scholar who found Antonio's lost notebook; and then, swapping tenses, tells us about the vegetation in Tuscany that spring: "The fig-trees are in bud, the terraces smell of wild marigold, and in sheltered spots the first olive-blossom is out: tiny yellow flowers, foretelling the harvest to come."

It's lovely stuff: the Latinate tag, the easy erudition, the thoroughness of it all. But Nicholl's sidestep into nature is also worrying. If you've read Panofsky, you'll know the iconological language of flowers; if not, Nicholl's analysis of the Benois Madonna spells it out for you. Pondering the bloom in the Benois Christ-child's hand - "According to the botanist William Embolden, it is probably the bitter cress, Erica sativa" - Nicholl unpicks the flower's meaning: "The child contemplates a symbol of his own future agony. The mother who smilingly proffers [it] does so unknowingly; she is shielded from her tragic future as the child is from his." Flowers - bitter cress, olive blossom - foretell the lives of gods; and the infant Leonardo, like the baby he will paint, is a god.

It's bad luck for Nicholl that his book should appear so soon after the worldwide success of Dan Brown's novel The da Vinci Code: bad luck, because you'd expect a good biography to counter the kind of cultic twaddle on which Brown trades. The trouble is that if you ignore the various cults of da Vinci - Vasari's, Lomazzo's, Brown's - then you're left with precious little to work with.

Not for nothing were Leonardo's favourite animals birds and bats, creatures that, in his phrase, "flee from one element into another". As soon as he could, the bastard boy from Vinci left for Florence. By the time he died 50 years later, he had lived in Milan, Rome, Mantua, Venice, in Florence again and then, finally, over the Alps in Amboise. Along the way he left meagre traces of his life: a grandfather's birth-record here, a denouncement for sodomy there.

The overwhelming mass of information on Leonardo comes from the 6,000 surviving pages of his notebooks. Written back-to-front and cryptically - "When Fortune comes sieze her in front with a sure hand, for behind she is bald" - these are long on brilliance but short on fact.

Such brief dips into autobiography as Leonardo takes are bound up with a sense of his own myth. The famous kite story, in which the artist recalls a bird sitting on his crib and tapping his mouth with its tail, is so patently false that it's hard to know what to do with it. Freud based a whole sex-and-death theory on the bird, carelessly translating nibbio (kite) as "vulture" and making an arse of himself in the process. It's a warning to be heeded by the wise.

So what, as a good biographer, do you do? Well, probably what Nicholl has done: namely, flesh out those bones with such certainties you can find: catasti, Linnean names, lists of possessions, social history. You travel to the places Leonardo travelled to and you imagine them now as they were then. Nicholl has worn out his boots tramping around Monsummano, a hill near Vinci that may appear in Leonardo's earliest extant landscape, looking for the place from which it was drawn. "My own belief," he finally concedes, "is that no such spot exists."

So, tentatively, remembering the Freud débacle, you end up playing the psychoanalysis card. At times, Nicholl does this brilliantly. His suggestion that the prominence of St John the Baptist in Leonardo's Holy Family groups can be put down to the artist's identification with the excluded child accounts for the yearning in these pictures. That the curious absence of St Joseph from them springs from Leonardo's bastardy rings true as well. On the other hand, Nicholl's citing of a fragment translated by Carlo Pedretti - "You will have sex with your mother and sisters" - is so clearly cuckoo that you sense he's clutching at straws.

And that, in the end, is the problem. Nicholl has written two distinct and unsatisfying books here: one that picks over a skeletal past, another that tries to ground that past in the present. Occasionally, fate does him a kindness: a British parachutist who runs up a parachute to Leonardo's 500-year-old design and jumps with it successfully; a Leonardesque bridge built, five centuries after the event, in Norway. Mostly, though, Leonardo da Vinci: The flights of the mind remains a book of two halves, its subject as unknowable as he's ever been.

Buy any book reviewed on this site at www.independentbooksdirect.co.uk - postage and packing are free in the UK