Built up and torn down by the tabloids way before Britney made us sick of wax jobs, ROBERT DOWNEY JR is a gracefully-aging hippie with a story. Lucky for us, he gets to channel his demons in what looks to be this year's ironclad blockbuster.

First off, the trailer's amazing. If you haven't already seen it, you should proceed to YouTube and play the Iron Man trailer before reading further. It's got fireworks and bangin' hard rock from the likes of Audioslave, AC/DC and Black Sabbath. The CGI is pretty cool and the suit's not corny (phew) and all that, but pay special attention to Robert Downey Jr's comic timing. It's not immediately obvious, which makes it all the more impressive. He's got a steely flamboyance beneath those liquid-brown boyish eyes. And his throwaway lines - crackling with wit, repartee and laughable sarcasm - we suspect, were not in the script. Spectacular trailers and cool lines: It's the stuff legendary summer movies are made of.

The 42-year-old New Yorker is, after all, the pin-up for Hollywood excess, an enduring symbol of how fame and riches can derail so quickly. A resume of 50-plus films did nothing to prevent the substance abuse. Having served a year's hard time in state prison in 1999 for drug and alcohol-related offences, Robert Downey Jr. is ready for his leading-man comeback. Again.

But the initial reaction to Downey playing the iconic crime fighter was, weIl, lukewarm, accompanied by lots of head-scratching. Put it this way, he's not the comic geek's natural choice. Prior to Iron Man, his most successful films have been Wonder Boys, Chaplin (for which he received an Oscar nomination), Kiss Kiss, Bang Bang, and more recently, A Scanner Darkly, Good Luck And Good Night and Zodiac.

Basically, until now, he's been that left-field, kinda-gayish, born-again-gypsyish sorta guy who hasn't hit real paydirt in any genre - yet. That' s what you call someone who throws himself into martial arts, therapy and obsessive weight-lifting to prepare for the role. Iron Man fans had to Google his name to call up his mug. Did he have the chops to play the hard-bodied Tony Stark, an arms manufacturer who uses his jet-powered, missile-launching suit of armour to fight eeeeeevil? But it's exactly this wayward charm - this pre-Lindsay, Britney and Paris drama-queen behaviour - that lends a curious cachet to Downey. He was the original tabloid subject, back when gossip sites - without the aid of video and sound - were merely bitchy forums.

Iron Man director Jon Favreau said, "We didn't want to go with a safe choice. The best and worst moments of Robert's life have been in the public eye. He had to find an inner balance to overcome obstacles that went far beyond his career. That's Tony Stark. Robert brings a depth that goes beyond a comic-book character who is having trouble in high school, or can't get the girl. Plus, he's simply one of the best actors around."

And Downey seems to be holding up his end of the bargain. From a physical viewpoint, he's done a lot of the motion-capture work for Iron Man himself. He's putting his back into the weights. He pulled the production shifts with two other guys, taking turns to wear the too-heavy Iron Suit (when close-ups weren't needed, it was his stunt doubles doing the heavy-lifting) . He's also done the promo rounds and aced the convention floor at Comic Con, the focal point and courting grounds for Alpha geeks everywhere. And he told LA reporters last year, "I went after the role like a greyhound after a rabbit. I'm more diligent than I used to be. I want to show Jon he was right to have faith in me. Whatever questions which might have arisen about my life weren't issues with him." He was also quoted in Entertainment Weekly saying, "The physics are pretty simple - if you're not shooting yourself in the foot, you're gonna have better opportunities. Nowadays, it's like the quantum leap from instant stardom to instant bad boy or girl is so quick. For me, it was a really slow burn. Rut it's really just a function of age, you know?"

More tellingly, Downey had not had to audition for a role since Chaplin. But he screen tested for Iron Man. He told Esquire last year, "Why am I the guy for the job? Because the story is the most duplicitous and conflicted of all the Marvel characters, because he's really just a guy who gets put in an extraordinary set of circumstances, partially due to his own character defects and partially due to his lineage... and there's nothing I could bring more to than this job and story." Well, he sounds determined to make the trilogy work.

For what is a film that has yet to steamroll the buzz it deserves - Indiana Jones and the Kingdom of the Crystal Skull seems to be carpet-bombing the press right now - Iron Man looks certain to be the sleeper hit of Summer 2008. There are two levels of public interest in the film. 1) That it's the first of a US$165 (S$230) million-a-pop movie franchise, big enough to rival the Dark Knight and X-Men, and 2) It's a celluloid, comic-book translation of Robert Downey Jr's own dark past, realised with a sharp script, a stellar cast and a Hollywood budget. While the families and tweens will be going into the darkened halls for gratuitous special effects and explosions, the tabloid set among us will be seeking the shades of truth in Tony Stark. One full year in state prison scars you deeply enough to release something maniacal. And that might just be what the year's best popcorn movie is made of.