Anybody who thinks he or she knows about cinema thinks he or she knows about Orson Welles. At the time of his death in 1985 it was fashionable to argue that Welles had lived his life backwards. If the poles had been correctly aligned, Orson would have begun by selling port in cheesy commercials, gone on to low-budget independent films and finally – offered full creative support by the studio – delivered a masterpiece in the form of Citizen Kane. (The very early years spent bluffing his way around the Gate Theatre in Dublin don't fit comfortably into either timeline.)

Over the intervening decades, that convenient conceit has frayed a little. The reputation of later films such as Touch of Evil and Chimes of Midnight has soared. The final struggles have taken on an increasingly heroic quality. Next year we hope to see a delayed reconstruction of his final film The Other Side of the Wind. But we do still know one thing. After two pictures for RKO, Welles was shunned by Hollywood because he was difficult, profligate and unconventional. Isn't that right?

Compulsive

Watching Chuck Workman's compulsive documentary Magician: The Astonishing Life and Work of Orson Welles, released in the year of Welles's centenary, one is, once again, confronted with the inadequacy of that reading. Hollywood groaned with primadonnas, tyrants and spendthrifts. Welles was famously charming. His first two films, Citizen Kane and The Magnificent Ambersons, did not go wildly over budget. When one considers how tolerant Warner Brothers was with Stanley Kubrick, it remains even more baffling that Welles never made a film for one of the six major studios.

“He wasn’t really difficult,” Workman says. “That’s right. He just didn’t want to compromise. He couldn’t understand what the point was of going through what you have to go through to make a film if you are going to just toss it off. One answer is that there just was no independent film-making in those days. The studios had to make money.”

David Thomson, Peter Bogdanovich and Barbara Leaming are among the dozens of distinguished writers to have tackled Welles’s story. The actor Simon Callow, who is interviewed at length in Workman’s film, is currently completing the third volume of a biography. None satisfactorily solves the question of why Welles was so comprehensively shut out of Hollywood.

Citizen Kane may have lost the best picture Oscar to How Green was My Valley, but it was still highly celebrated on release. The problems set in when the studio – unable to contact Welles while he was shooting the documentary It's All True in South America – eviscerated his adaptation of Booth Tarkington's family saga The Magnificent Ambersons. In Workman's film, we hear Welles argue that this dispute poisoned relations between the studios. "I never recovered from that attack," he said. "Printed on every piece of paper that went out from RKO was 'Showmanship Instead of Genius'. In other words, the reason you should buy an RKO picture was that you didn't get Orson Welles."

Singular life

All of this contributed to one of the great myths in American culture. So weird and diverse was Welles's career that it is hard to locate points of comparison with any other director. His life was more singular still. Born in Kenosha, Wisconsin, raised largely in Illinois, he seems to have sweated creativity from the moment he first stood upright. Magician locates a newspaper clipping declaring him to be "Cartoonist, Actor, Poet and only 10".

Nobody is sure exactly what age he was when he turned up in Dublin and charmed his way past Hilton Edwards and Micheál Mac Liammóir, guardians of the Gate on Parnell Square, but the phrase “boy genius” was already in the air. In archive footage, Mac Liammóir confirms that Welles was already a master of his own mythology: spinning scarcely believed tales about prodigious experience.

Back in New York, he somehow finessed his way to a key position in the Federal Theatre Project, an offshoot of FDR’s Works Progress Administration, and became the most energetic presence on Broadway. When the call “eventually” came to make his debut feature, he was massively celebrated, but still only in his mid-20s.

Rather than comparisons with contemporaneous film directors, we should perhaps gesture towards prodigious men of action such as Napoleon. Both men seemed implausibly energetic, insanely confident and endlessly charismatic. Both conquered most available territories before middle age loomed. Both were prepared to burnish their own reputations.

Creating a legend

Workman's film features an interesting debunking of one, relatively insignificant Welles myth. The story goes that, while working on a theatrical production of Around the World in Eighty Days, he ran into a budgetary crisis and, desperate for $55,000 (€49,500), phoned producer Harry Cohn for help. While in the throes of his pitch, he spotted a paperback novel on the desk, turned it over and read the title: If I Die Before I Wake. He told Cohn the novel (of which he knew nothing else) was sure to produce a hit and found himself adapting it into The Lady From Shanghai.

In Magician, we see Welles telling the story in several different versions and hear it wryly debunked by Peter Bogdanovich. So, to what extent was Welles a collaborator in the creation of his own legend?

“Look, he was being interviewed from the age of 10,” Workman says. “He was a prodigy. He was constantly in the spotlight from the age of 15. Even when he was in Ireland he was sweet-talking whomever. Of course he made things up. Who doesn’t? But most of the myths are true.”

That is the most baffling part of the whole story. In the 1970s, Pauline Kael, film critic of the New Yorker, famously tried to pull down the temple by suggesting that the contribution of writer Herman J Mankiewicz to Citizen Kane had been greatly underestimated. The mud didn't stick. Peel away the few half-truths and you still have an epic legend that defies easy comprehension.

“When I first came to Hollywood, in the 1970s, he had become this guy who had trouble fitting into cars after leaving restaurants,” Workman adds. “We thought of him as a different person to the man who made those films. But he wasn’t. He stuck to his integrity. He was never going to stop being Orson Welles.”

Magician: The Astonishing Life and Work of Orson Welles is on limited release. A new print of Touch of Evil opens at the Irish Film Institute on July 10th