Toback wrote Two Girls and A Guy for his friend over the following week,then shot the film in 11 days, before Downey went back behind bars. As a study of male selfishness, vanity and self-serving sophistry, Downey's wheedling womaniser is a triumph. But whether the character of Blake Allen says more about Toback or Downey is debatable. "I thought I was writing him," says Toback, "but he said that he was `doing' me."
Whatever the truth, Toback isn't perturbed by the suggestion that his slippery lead is a self-portrait. Unlike other film-makers who fight shy of reductive autobiographical parallels, Toback has always embraced the idea of living his life as a kind of wild, novelish fiction, while using his films to blur the boundary between reality and fantasy. "I barely find a distinction," says Toback. "I see my films as a continuation of what I'm thinking about, while my life is a preparation for the next film."
His unique style of pre-production began as a student at Harvard in the 1960s, where Toback "sought out extreme experiences". On one occasion, he decided to beat the world record for LSD, dropping a "psychotic amount of acid and losing all sense of identity", before a kindly biochemist ended his eight-day trip by injecting Toback with a cocktail of heroin and thorazine that glued his brain back together.
Before his 28th birthday, he had married and divorced an English aristocrat and developed a ferocious gambling habit that would introduce him to a criminal underworld (dramatised in both 1977's Fingers and 1991's Bugsy) and mire him in debt to the tune of $1m.
"I do get excited by what other people would consider to be reckless behaviour," admits Toback. "I may be chemically addicted to it. I've had a few near-death experiences. I like it when the stakes are high."
After graduating, Toback began teaching at New York's City College and contributing articles to magazines. Assigned to write a piece on football- player Jim Brown, he disappeared into the sportsman's mansion where he swapped lectures for drug-fuelled orgies. When he surfaced, two years later, he wrote his first screenplay: The Gambler.
Part Dostoevsky, part autobiography, the film starred James Caan as a risk-addicted academic. With characteristic hyperbole, Toback sees it as his salvation. "If Karel Reisz had not chosen to direct The Gambler, I don't think I would have had a career in film-making. Left to my own devices, my naturally chaotic and provocative instincts would have long since led me to some catastrophic consequence. I think I would have been dead by now."
Toback's self-mythologising might seem pathetic were it not for the director's determination to translate his existential hell-raising into equally risky cinema. To date, Toback's attempts to put his student experiences on film in Harvard Man have foundered (although a pre- Titanic di Caprio was "dying to do it", Toback's script was turned down by 10 studios). But a succession of other, highly personal movies have confirmed critic David Thomson's description of Toback as "America's most uninhibited film-maker", an auteur unafraid to risk life, limb and pretension to root out larger truths.
Take his ambitious 1989 documentary, The Big Bang, which saw Toback rounding up a group of 19 talking heads (including an Auschwitz survivor, a movie star and a gangster) to talk about love, sex, death and the whole damn thing. Not all such gambles have paid off: Exposed's story of an international model (Nastassia Kinski) caught between terrorist Harvey Keitel and violinist Rudolph Nureyev springs to mind. Still, you can't help but admire Toback's willingness to stake his soul on such "serious and original" film-making.
In Two Girls and A Guy, Toback once again cannibalises his own experience - this time as a shameless philanderer (Spy magazine once devoted a double- page spread to Toback's chat-up lines, which tragically included "I work closely with Warren Beatty") - to explore wider themes of monogamy and masculinity. Hot on its heels comes Black and White, "a movie about race, sex and identity" starring Brooke Shields, Downey Jr, Mike Tyson and the Wu Tang Clan, inspired by Toback's time "as the only white guy" at Jim Brown's house.
"A friend asked me, `do you realise the storm this is going to cause?'" laughs Toback. "He said, `when the film comes out, you're either going to have to stand in the middle of a volcano, or go into hiding'." No guesses which Toback will choose.
`Two Girls and A Guy' opens on 29 January