The decade 1933-43 was one of busy erotic multi-tasking by the deft and diminutive Pablo Picasso. It took him the best part of ten years to effect a separation from the reluctant Olga Khokhlova, his ex-ballerina wife, retired injured from the Diaghilev Ballets Russes. Legal proceedings were triggered by her discovery of Picasso’s affair with Marie-Thérèse Walter (aged 17 when Picasso picked her up in 1927 outside the Galeries Lafayette). On 5 October 1935, Marie-Thérèse gave birth to Picasso’s daughter, Maria de la Concepción, later known as Maya. By then Picasso was fornicating on many fronts: with Alice Paalen, the wife of an Austrian painter, and the 49-year-old Valentine Hugo, an ex of André Breton. Picasso disencumbered himself of both relationships when he took up with Dora Maar (Henriette Théodora Markovitch), the half-Croatian, half-French surrealist photographer.

But he persisted with Marie-Thérèse contentedly and comfortably, setting up her and her sister and mother in the Villa Gerbier de Jonc in Royan, where he spent homely weekend rustications – escaping Dora’s jealous hysteria and subsequent self-reproach. His continued relations with Marie-Thérèse destroyed Dora’s amour propre but piqued her sexual masochism. (Her masochism seems to have been refined and educated by Georges Bataille in a previous relationship lasting five months.) There was, too, the odd bonk with Nusch Éluard, the wife of the poet and Picasso satellite Paul Éluard, who was himself broadcasting his seed in several furrows. At the end of Volume IV of John Richardson’s biography, subtitled ‘The Minotaur Years’, Dora Maar is dumped after seven years – quite a long time – and takes her moodiness and tantrums for analysis with Jacques Lacan, later to be a famous theoretician of unmatched obscurity. Picasso then turned his attention to the 23-year-old Françoise Gilot, by whom he fathered two children, Paloma and Claude.

The interesting thing is that, although we know all this, we actually know very little. Picasso strove to keep his private life private. He took unsuccessful legal action against the memoirs of Fernande Olivier (his first love) and Françoise Gilot. He succeeded all the same – because of his own silence. He gave away very little, which means that Richardson and others are compelled to deduce his interior life from his self-portrait as minotaur – wounded, dying, domineering, mythic, various, enigmatic. Picasso said that his paintings were autobiographical, a diary of sorts, but they are a diary in disguise. They promise revelation yet don’t deliver it. They are a tease, an invitation, as it turns out, to invent your own narrative.

For example, his portrait of Dora Maar, ‘Weeping Woman’, tells us nothing about why she is weeping, nor what precisely Picasso felt about it. He gives us the drama of tears and the brilliant graphic detail of the chewed handkerchief – an index of her pained effort to stop crying. The worldly Heine said: ‘No matter how much you cry, in the end you have to blow your nose.’ Picasso’s depiction says nothing so comic or cynical or explicit or knowing. The woman is in the storm of feelings, buffeted, helpless, in a state of total immersion, unreachable. We have all been there – excluded by another’s pain. We assume that Picasso tired of these tantrums, but we can’t know that. She apologises, promises to reform. Picasso seems to have persevered patiently enough – seven years! – while equally persistently caring for Marie-Thérèse. Not quite the monster minotaur as advertised. He valued, it appears, Dora’s intelligence, her sophistication and her ability to speak Spanish, a skill from her childhood in Buenos Aires.

At the same time, these are the years of the Spanish Civil War and the second world war. Richardson, like others, cannot believe that such cataclysmic events do not leave traces in the art. Accordingly, pictures are pressed for private disclosures and public positions – unpersuasively because simultaneously. It’s a version of spreading your bets, of insurance. A painting of Charlotte Corday stabbing Marat in his bath is at once a depiction of Olga stabbing Marie-Thérèse and a reference to the Night of Long Knives in Nazi Germany.

Even the clearly public, overblown, bombastic, op-ed, engagé ‘Guernica’, with its urgent outraged banalities, is meted its quota of insider ‘personal’ touches. Dora Maar’s later commentary is mainly an exposition of her contributions to the painting – the reference to her photographic lighting equipment; her short vertical brush strokes to differentiate the horse’s body and legs. Richardson quotes Luis Buñuel’s jaundiced verdict: ‘I can’t stand “Guernica”, which I nevertheless helped to hang.’ Buñuel was uncomfortable with its ‘grandiloquent technique’ and ‘would be delighted to blow up the painting’. When Picasso was given the commission, he said he ‘had no idea what a bombed town looked like’. Which is why the painting chooses the mythical-classical ersatz substitute, a soft surrogate of cartoon emotion, lent the feel of reportage by the greys and blacks of newsprint. For Richardson, it is a masterpiece.

Although Richardson now and then expresses a few token blanket, non-specific dismissive verdicts, his default judgment is the gullible short cut of ‘masterpiece’. His attitude to Picasso’s ‘poetry’ can serve as a benchmark: ‘The ambivalence of his writing – the love and fear, tenderness and cruelty, laughter and tears – entitles the artist to be recognised as a formidable surrealist poet.’ Sample:

Cries of children cries of women cries of birds cries of flowers cries of wood and stones cries of bricks cries of furniture of beds of chairs of curtains of casseroles of cats and papers cries of smells that claw themselves of smoke that gnaws the neck of cries that boil in cauldron…

The template here is the Greek pastoral elegy, where the poetic fiction is that the whole of nature mourns the dead person. But Picasso’s poem is a travesty of pastoral hyperbole – dull, overstated, repetitive doggerel cognate with ‘Guernica’.

Compare the critical laxity passim:

A drawing as factual as a diary entry, made on 1 August, depicts Dora inserting a key in Picasso’s door, symbolically entering his life, suitably dressed in a coat and headscarf. Picasso awaits her in the guise of a Greek god, a stick in his right hand and a dog clutched in his left.

In fact he isn’t clutching a dog. It’s in his lap and he’s feeding it from his hand. Sub-standard work is over-praised. Richardson describes a perfunctory sketch of Éluard as ‘Ingresque’. He means only that it is conventionally realistic. It is a world away from Ingres’s meticulous conviction, his detailed, unerring accuracy of observation, the unhesitating certainty of his intricate line. There is a second-rate surreal Picasso etching, ‘Two Figures on a Beach’ (1933), which features disjecta membra: on the right, the replacement of a ribcage by the slats of a shutter; on the left, a door which may also be a guillotine. An effortless dud, given a free pass by Richardson.

The real criticism comes from Richardson’s personal role as a minor courtier, the handsome boyfriend of the collector Douglas Cooper, gradually but unmistakably irked by Picasso’s settled air of superiority. The Picasso he gives us is a cruel egotist, a man familiar with suppliant abasement, insufferably accustomed to a kneeling acquaintance. This was the painter who signed his early work ‘Yo el Rey’ (I the King). However, isn’t there an irony here, a self-deprecating allusion to the Havana cigar, ‘el Rey del Mundo’? There is a telling anecdote about Picasso in the Hotel Vaste Horizon at Mougins, where the toilet facilities were shared: ‘One morning [the Hungarian writer Joseph] Bard bumped into Picasso leaving the loo.’ He tried ‘to back away in order to return later’. Picasso wasn’t having it. He ushered him into the lavatory and wiped the seat with a large silk handkerchief – ‘laughing and bowing, he closed the door behind him’. This is the throne Picasso sits astride.

Long though it is, Richardson’s Life was never intended to be definitive since many important archives are still closed. Nevertheless, it is an anthology of memorable gossip from the margins of Picasso’s life. We learn that Misia Sert was a morphine addict, and that her treachery to friends resulted in the nickname ‘Aunt Brutus’. We learn, too, that Caresse Crosby invented the modern bra, and that Salvador Dalí almost asphyxiated himself while giving a lecture in a faulty deep-sea diving suit. In 1929, Michel Leiris, a fervent Picasso acolyte, was depressed by his expulsion from Breton’s circle of surrealists and medicated his sexual hang-ups with alcohol. He appeared on George Bataille’s doorstep intoxicated at 5 a.m. asking for a cut-throat razor to castrate himself. Bataille fobbed off his request with the excuse that he only used an electric shaver. We learn that Lee Miller, beauty and photographer, was ‘adored by her lovers but few others’; that Picasso loathed flowers but loved vegetables; that the bombing of Guernica was a birthday present for Hitler from Goering; that Picasso suffered from sciatica but was cured by a Dr Klotz, whose expertise involved the cauterisation of the nasal nerves ‘to alleviate pain elsewhere’. All welcome additions to the Picasso story.