For Robert Downey Jr, prison is a lot like Hollywood. After getting into a jailhouse scrap and spending five days in solitary confinement, he found himself stood before one of the prison screws. He recalls, "I hadn't had a shower in five days, I was sleeping in my clothes, my hair was all ****** up. And then this guy came in and said..." Wait for it. "He had a script about unicorns. But it wasn't just your usual unicorn script."

It's as surreal as any scene from his latest movie, The Singing Detective, which probes the tormented mind of a writer (watch out for the unicorn scene!). And who better to do 'tormented artist' than Robert Downey Jr? The headline "Downey Arrested On Drugs Charge" has been run so many times it's become tired and needs a hit of cocaine just to get it through the day.

But while Downey's asking price has dropped, his career has never been in danger of getting flushed down the u-bend. Even doing porridge at a Los Angeles correctional facility didn't stop him working. In 1998 he was granted day release to shoot scenes for serial killer flick In Dreams.

The fact that In Dreams stank worse than Bob after five days in solitary confinement is beside the point. For the Hollywood set, the actor's drug-induced aberrations appear to be nothing more than an inconvenience. But I shouldn't be so quick to point the finger, because it's also one of the reasons we moviegoers find him so compelling to watch.

It's the old James Dean complex. Come on, don't deny it. You don't want Robert to get well! You want to be able to peer over the edge into oblivion, and you like to think it's there in his (glazed) eyes when he looks down the camera lens. That applies whether the camera is manned by a Hollywood DP or the LAPD.

Even Junior himself fears his talent is inextricably linked to his self-destructive tendencies. "I think the openness that might be necessary to be a good actor can be lethal in your real life," he reflects.

But self-destructive behaviour only works for so long before one of two things happens: 1. You die (duh). Plus, James Dean already has that base covered. 2. You become emotionally stunted and make cynical film choices.

It's fair to say Robert Downey Jr has made good money being lazy (consider US Marshals and Air America), but I like to think The Singing Detective will place him firmly on the upswing. The angst is still rife, as it needs to be, but playing a so-called "human pizza" is also a risky career move. And as long as Downey's taking risks with his career instead of his life, the future looks golden (and Oscar-shaped).

Downey doesn't need to be told, though, as he muses, "I'd rather wake up in jail for a TB test than wake up another morning knowing I have to go to the set of US Marshals." Enough said.

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