Ringmaster and star of his circus

The 20th century's artistic colossus was 'larger than life yet human'. Alex Danchev revels in his dazzling glow.

Pablo Picasso (1881-1973) is an industry and an archetype. His very name is a byword for the artist-creator. Within living memory, perhaps only Orson Welles combined the creative genius and the magic arts with such Mephistophelian glee - the facility and the mastery, the ingenuity and the prodigality, the daring and the devilment, the showmanship and the one- upmanship. Picasso's rapacious gaze and voracious ways are the stuff of legend. To show him a painting was a dangerous game. He would steal its secret in a second, and make it his own.

John Richardson makes a verb of this: "to Picassify". Picassification came easily to him. Negligently, he could turn out a masterpiece in an afternoon. And another. And another. He is the most prolific artist in recorded history. He mastered any medium. His photographs, illustrated here, are fascinating; his sculptures, brilliant improvisations on found objects, are sensational. The sculptures alone put him in the pantheon. He could also paint a little. In the awesome power of his artistic personality, he bestrides the 20th century like a colossus.

A stubby colossus who never learnt to swim (contrary to his boast), he mimicked the strokes while keeping his feet on the bottom. Picasso is larger than life, but human, all too human. One of the several pleasures of this biography is the sense of privileged access to the private Picasso - the one behind that formidable front - the mimicking of strokes, the up- keeping of appearances, the nursing of grievances, the jealousies, the rivalries, the sorrows, the rage.

The structure and texture of this volume will be familiar to aficionados of its predecessors. Each chapter is a more or less self-contained episode, meticulously crafted ("The Ballet in Spain", "Death of Apollinaire", "Summer at Juan-les-Pins"). They can be savoured (or devoured) as so many morsels of mouthwatering social history and as a sort of gazetteer of Europe at play, a Who Was Who? of the avant-garde, the beau monde, the gens chic and gens louche , as Richardson says characteristically, complete with social pedigree, sexual orientation, liaisons of every kind, deliciously specified - Picasso tickling a dancer's nipples with his brush - as told to the author.

And this author has unbeatable credentials. John Richardson knows these people. He was one of them. In more senses than one, he has lived the life. Most importantly, Richardson knew Picasso and his circle and had the opportunity to observe the artist, at work and at play, over the last 20 years or so of his extraordinary bid to beat mortality.

That experience and that entrée lend Richardson's account an authenticity and an intimacy that is hard to match or to dispute. For a biographer, these are priceless assets. A connoisseur of fine art and human foible, Richardson is both recorder and gossip, stylist and memoirist, scholar and sophisticate. He has a certain idea of Picasso. He serves it up, martini- like, with a twist.

The work is Picasso-centric, as the authorised biography of Winston Churchill is Churchill-centric. All biographies centre on their subjects, of course, some more slavishly than others. Some have a tendency to mirror their subject's self-absorption or self-conception.

Like Churchill, Picasso created around himself a kind of travelling circus to meet his imperious needs, a circus in which he was both ringmaster and star turn. Richardson's insider status, and skill in the telling, enables us to see how he did it. We get to know who was there, what went on behind the scenes, how it worked; we see anatomised the thrilling, gruelling high-wire act that is great art. The sawdust and tinsel of the life is consummately portrayed. The meaning of the life is more difficult to discern. There is not much weighing or assaying here. Long-range reflection is at a premium. Richardson makes occasional glancing connections, back and forth, but for the most part it is all arrestingly here and now. The daily round crowds out the examined life.

Criticisms and contrary opinions are reported, though not much explored, and very often extenuation is offered, as for example in the matter of the artist's ostentatious embourgeoisement - widely regarded as a sell-out by his peers - on which Richardson concedes that Picasso did have a bourgeois streak, but adduces also his "sardonic nature" and "penchant for self- mockery". For an author who describes one authority's thesis as "novelettish twaddle", and dismisses another with a magisterial "I doubt it", his own criticism of the art and the artist is noticeably mild. "Somewhat prosaic" is about as trenchant as it gets; "an unwonted whiff of surrealist contrivance" a more typical note.

Yet Richardson is no pushover. His learning is lightly worn, and the detailed reconstruction of the life is a remarkable achievement, too easily taken for granted. The work is among other things a prodigious feat of research, in published and unpublished sources on every continent. If the superstructure bears Richardson's inimitable signature, the base is a tribute to his long-standing collaborator Marilyn McCully, a powerhouse of scholarship and intelligence, at home in everything from the old and new room numbers of the Savoy Hotel to the dating and attributing of paintings.

So rich is this volume, so dazzling its surface, that the larger claims it makes and the wider questions it raises may go begging. The thesis of this slice of the life is that it was the most innovative since Cubism in the years before the Great War. The breakdown of the work makes it almost impossible to assess that contention, just as it is almost impossible to evaluate such intriguing obiter dicta as "the principal influence on Picasso would be his own earlier work".

Three volumes so far have given us half a life. A fourth is foreshadowed for the rest. Guernica (1937) is not yet in sight. How to slice a life? Will the great prestidigitator slip through the fingers?

Alex Danchev is professor of international relations at Nottingham University, and the author of Georges Braque: A Life (Penguin, 2007).