What if Robert De Niro threw a film fest in his Manhattan backyard and everybody came?

At film festivals, as in movies, you’re usually made to wait for the climax — suspense and anticipation are their own reward, or so goes the theory. In other words, pace yourself, take small bites, and no dessert before dinner.

But just try telling Robert De Niro how to set his table. On May 8, with New York’s City Hall behind him (literally and figuratively), the actor and co-owner of the Tribeca Grill premiered his latest creation, the first Tribeca Film Festival, with some characteristically terse — but altogether heartfelt — words about reinvigorating the post-Sept. 11 economy of lower Manhattan. And yet, as fascinating as it was to hear the semimythic De Niro speak live in public (which seems to rank just above ”You talkin’ to me?” jokes on his list of Great Loathes), the crowd’s attention was drawn to a dais so sumptuously freighted with luminaries it had to be in violation of the fire code.

And that’s not even counting featured speaker Nelson Mandela. The former South African president was escorted by Whoopi Goldberg, looking humbled to find herself in the Center Square of the global A list. At this point, even the unflappable Kevin Spacey turned tourist, snapping his fellow guests with a digital camera. Who can blame him? How many festivals can boast opening ceremonies with a Nobel Prize winner, a presidential aide (Chris Henick), ex-president Bill Clinton, and Godfather Francis Ford Coppola?

But how, you may ask, do you follow an act like that? Why, with Hugh Grant, of course! ”There’s an element of bathos,” admitted the actor, who spoke shortly after Mandela and reminded everyone, with some well-placed self-effacement, that this was, in fact, a film festival. (”A fabulous vitamin B12 shot to the buttock!”) Grant’s About a Boy, which was produced by De Niro and festival cofounder Jane Rosenthal’s Tribeca Productions, kicked off the May 8-12 fest with a red carpet flush with Hollywood royalty, including one of Tribeca’s celebrated jurors, Helen Hunt.

At the after-party in the ballroom of the Regent Wall Street hotel (a landmark former bank and the venue where Liza Minnelli and David Gest held their reception), there was no discernible VIP room, as everyone was a VIP — at least in their own minds. There was even an indie-versus-downtown-fabulous clash of the titans when supermodel Heidi Klum gave a quick German (and Film 101) lesson to a chiseled partygoer after he shook hands with Wim Wenders. ”You say Wim Wenders with a V!” she corrected over the techno. ”Veem Venders. It’s German.” To which the man replied blankly, ”He’s a director, right?”

Not that the Tribeca Film Festival clung too fiercely to indie credibility. If it had, its directors probably would have passed on screening Divine Secrets of the Ya-Ya Sisterhood, starring Sandra Bullock, Ellen Burstyn, Ashley Judd, and Maggie Smith. Though plenty of Golden Girls-era women were in attendance at the finger-sandwich tea party at Bubby’s, an upscale down-home eatery, the Ya-Ya factor was low, and Burstyn gracefully bore the publicity brunt, proffering explanations as to why a studio film about Southern women should feel at home, y’all, at an ostensibly independent New York film festival. ”This movie is smart and funny with complicated characters, just like New York is,” said Burstyn. ”Besides, I live upstate and need a break from writing my autobiography.” Despite minimal grousing from local filmmakers about Hollywood films ruining the artistic integrity of Tribeca (already there were flyers for a ”fringe festival”), the screening for Ya-Ya was standing room only.