It was not, to borrow from one of the film's most famous lines, an offer he couldn't refuse. Coppola feared it would glorify the mafia and reflect poorly on his own Sicilian heritage. It was not as if he was the first choice: Sergio Leone had declined; so did Peter Bogdanovich. Even when Coppola did go on board, he disagreed wildly with Paramount, which was set against him casting Marlon Brando as patriarch Don Vito Corleone.

"I was always on the verge of getting fired," he says. "It was an extremely nightmarish experience."

Perhaps the only delight was that he got to work with his father, composer Carmine Coppola, who collaborated with Nino Rota on the score. But with a young family to support, the director was heading for a meltdown. "I thought was a total failure, and everyone told me it was." To escape the furore, he went to Paris to work on a script for Jack Clayton's 1974 version of that he'd been commissioned to do.

When he returned, he was the toast of Hollywood.

By the end of 1972, had become the all-time box office champion, with estimated worldwide grosses of US$150 million. "I was shocked to see how it hit in that way," says Coppola, who owned a six per cent stake in the movie. He became an instant millionaire. The film also won him two Oscars - including for best picture. " changed my life, for better or worse. It definitely made me have an older man's film career when I was 29."

At first, it didn't. He - briefly - became that European-style director he so craved to be, when he got to make , a sublime piece starring Gene Hackman as a surveillance expert that arrived in the midst of the Watergate scandal and was influenced by Michelangelo Antonioni's . Written in the mid-1960s, Coppola had been trying to make the film for years - and suddenly he had some major leverage. "After , they said, 'Well if you make another film, you can do that.'"

As trade-offs go, it's what you might call a win-win situation. won Coppola the Palme d'Or in Cannes. Then, to fulfil his obligation, he made 1974's . Even now, 40 years on, it remains a towering achievement, from fleshing out the back story of a young Vito Corleone (played by Robert De Niro) to deepening the themes and characters as Corleone's son, Michael (Al Pacino), rises to power.

Another six Oscars, including three for Coppola, mean it remains the greatest sequel of all time.

At this point, Coppola's reputation - unfounded, he says - for megalomania swelled as he ploughed into his own heart of darkness making , his surreal, stunning take on the Vietnam war. Everything from set-busting typhoons to a heart attack for leading man Martin Sheen sent the film way over budget and schedule, forcing the director to pump US$25 million of his own money into the production, as he mortgaged the wine estate in Napa Valley that he'd purchased in 1975.

He called it his own "idiodyssey".

When finally emerged in 1979, it shared the Palme d'Or in Cannes with Volker Schlöndorff's . But Coppola denies it capped the end to a remarkable decade. "A lot of people say to me: 'How do you feel? Your movies in the past were so successful.' My movies were never successful! got terrible reviews! Read the review of - arguably my most successful film."

Indeed, the trade paper dubbed it "occasionally confusing", "overlong" and "never so gripping as to be superior screen drama".

There was worse to come: , his highly stylised 1982 Las Vegas-set musical, went millions over budget and forced Coppola to file for bankruptcy. Then in 1986 his 22-year-old son, Gio, died in a speedboat accident.

Coppola found no solace in work either. Flops, such as jazz-era gangster film , were followed by sell-outs, such as the limp

By 1992 he listed his personal deficit at US$98 million - though turning entrepreneur (wine, cigars, hotels) helped push him towards financial solvency again. But his work began to slip, reaching a nadir with 1996's man-child tale , starring Robin Williams. A director for hire on the 1997 adaptation of John Grisham's , it took a decade before he returned with 2007's , a low-budget film that took him back to his pre- days, back to that European-style director he'd always wanted to be.

He's made two more films since, and , but - at age 75 - he may never direct again. Last credited on daughter Sofia Coppola's 2013 film, , as an executive producer, there's still no sign of his long-gestating sci-fi . While that got too expensive to produce, he has no regrets. "It's good to be overly ambitious. I think it's better to be overly ambitious and fail, than to be under ambitious and succeed in a mundane way."

The Godfather The Godfather: Part II