In one sense, Isidore Isou had been predicting the events of May 1968 for nearly two decades. The Romanian-French artist and poet, founder of the avant-garde lettriste movement, had been calling for an uprising of the youth since 1949, when he and his followers plastered the Left Bank with posters declaring, ‘12,000,000 YOUTHS WILL TAKE THE STREETS TO MAKE THE LETTRISTE REVOLUTION’. When the uprising came, however, the slogans on display were those not of Isou and his lettriste comrades but of the Situationists, a long-established splinter group led by Isou’s nemesis, Guy Debord.

As the rioting intensified, Isou attempted to assert control, demanding that the students recognise him as their leader, even attempting to gatecrash a radio programme to declare himself head of the French nation. The revolution, his revolution, was really happening, and yet he was confined to the margins. In a cafe, surrounded by comrades, Isou began to rave. He wanted to cut himself to prove to his followers that he was immortal. A doctor was called. Within hours Isou was in an asylum under heavy sedation. By the time he woke up it was mid-June.

In his manifesto of lettriste poetry, published in 1947, Isou states that ‘no word is capable of carrying the impulses one wants to send with it’. Words must cede place to letters as the primary vehicles for poetic expression. ‘Isou will unmake words into their letters,’ he declares (Isou is very much one of those people who talk about themselves in the third person). ‘Isidore Isou is starting a new vein of lyricism. Anyone who cannot leave words behind can stay back with them!’ If you look online, you can hear him reading some of his lettriste poems. They are arresting, sometimes even thrilling: a barrage of coughs and hisses and guttural rasps, marked by the occasional interruption of a recognisable name or phrase. Not a million miles from Dadaist sound poems, then, though Isou’s megalomania meant that lettrisme’s relationship to any forebear was always tortuous, jealous and vigorously contested.

Nevertheless, when the Dadaist poet Tristan Tzara was buried at Montparnasse in the winter of 1963, Isou and his followers arrived uninvited at the cemetery and fought with the communists who had also come to pay their respects. As Isou began to make a speech, he was informed that Tzara’s family had wished for the funeral to pass in silence. Undeterred, he began to declaim a lettriste poem: ‘étli, tzara, jofué lochigran télebile sarkénidan.’

As Andrew Hussey puts it in his enthralling new biography, Isou is ‘grandiose, exasperating, self-regarding, brilliant, piercing and poetic, often all in the space of the same page’. Isou’s heroic period, however, occupied only a sliver of his life, a brief thrill of youthful self-confidence that lapsed precipitously into bitterness, petulance and a career churning out under-the-counter erotica with titles like Les Orgies d’un séducteur and Les Plaisirs d’une dépravée. In telling the whole story, Hussey is forced (and forces us) to endure the long, painful decline of a messianic narcissist, in and out of institutions, perceiving enemies on all sides and kicking out at them in bouts of hysterical autofiction.

At times, Hussey understandably loses patience with his subject. As the narrative reaches the bleak 1970s and 1980s, paragraphs increasingly end with a kind of pathetic punch line:

Briefly Isou offered himself as a psychiatric consultant using the ‘new methods’ he claimed to have pioneered. He charged the same hourly rates as accredited psychiatric consultants. He had no clients.

Of a late radio interview, Hussey writes, ‘he went on to say that his only real rival in history was Leonardo da Vinci, but that Leonardo lacked Isou’s focus and creativity.’

Having once styled himself as an incorrigible, never-miss seducer whose sex manual (named after himself: Isou ou La Mécanique des femmes) features a method called le baiser Isouien (‘the Isou screw’), the aged Lothario eventually claimed that ‘he did not have the time any more for human relationships and it was more efficient to masturbate in a porno cinema whenever the sexual urge overtook him’. In his own mind, he had become too busy and important to involve other people in his sex life. The pathos is almost painful.

So why, then, should we care about Isidore Isou? Because for a time – the half-decade from 1946 up to and including the release of his scratched and scrawled-over film Traité de bave et d’éternite in 1951 – Isou, with his swagger, his film-star looks, his street smarts, his ferocious self-belief and his ruthless, shameless talent for self-promotion, was the prototype of the rock ’n’ roll idol. As Greil Marcus put it in Lipstick Traces (1989), ‘throughout his early and mid-20s [Isou’s] great role was to bring out the fanatic in anyone – especially in young people convinced of their own unacknowledged genius. In any time, this means a lot of young people.’ Furthermore, in his destructive pursuit of self-affirmation and his relentless attacks on whatever had come before, Isou inspired the Situationists, who inspired Malcolm McLaren, who inspired the Sex Pistols, who inspired a hundred thousand teenage bands. When he first arrived in Paris, twenty years old and having fled the pogroms of war-torn Bucharest, he inveigled himself into Gaston Gallimard’s office and through a combination of denouncement, chicanery and physical threats secured a two-book deal. Gallimard’s reader fretted that he could not see any indication of literary talent. He was wrong. Like the Sex Pistols, Isou’s talent was in (to quote Marcus again) ‘replacing civility with noise’.

Looking for clues as to where that messianic confidence might have come from, Hussey painstakingly reconstructs the Bucharest of Isou’s childhood: the huliganii, the nihilistic thugs with whom Isou ran in his teens; the plan (aborted at the last minute) to seduce and murder a young woman; the massacre Isou witnessed on the night of 23 January 1941, when he was captured by the rampaging Iron Guard. In the confusion of the pogrom, he escaped with his life; dozens did not. Hussey sees in this event the seeds of Isou’s fury: a contempt for the complacency of postwar reconstruction and for the return to old ‘Christian’ values.

For all of its telling projections forward, however, the section on Isou’s childhood is too long and too close to its sources in Isou’s own journals and memoirs. We are nearly halfway through the book before we reach the artist we recognise. Before that, we have learned that Isou once struck up a conversation with a stranger on a train, pretending to be a medical student; that a man called Iancou farted a lot; that, while passing through Budapest, Isou made love to a woman named Anna. Here, the biographer’s filter has stopped working. We sense the voice of Isou himself, always unreliable, the creep who needs to tell you everything: ‘When she finally climaxed, she seemed to melt, whispering “Isou-ou-ou” or “Isou-ou-ou-ou” with every breath.’ Did she indeed? Can we know? Do we need to?