Melvin Van Peebles - or Melvin Van Movies as Mario affectionately refers to his pa - is an esteemed director, screenwriter, lecturer and composer. But what strikes you most about Van Peebles senior is that he appears to have spent his 63 years sucking lemons. He leans back, forcing the breath from his lungs, and speaks through a mouth whose permanently downturned corners could only be raised by an industrial winch.
His eyes, too, seem to be fighting a losing battle with gravity, and with a bandanna stretched taut across his scalp, he has a weather-beaten gypsy quality. But there's no mistaking the sparks that dance in his eyes whenever he starts reminiscing about his directing career at the start of the Seventies.
However, raise the subject of Panther, the film he has adapted for the screen from his own novel, and he looks ready for cocoa and an early night. The movie tells of the Black Panther Party, the revolutionary black activist group formed in America in 1966 by Huey Newton and Bobby Seale. It's a lucid, linear picture, solidly directed by Mario, and if it seems to emanate more from lectern than trench, that's because it has a lot of groundwork to do: unbelievably, it's the first picture to address the Black Panthers' story.
"The Panthers are not part of the American consciousness," Melvin sighs with a weariness that suggests despair at this fact. Or boredom at finding himself in yet another hotel room talking, yet again, about a subject that has consumed him for nearly 30 years. Or, perhaps, both.
"I used to do concerts for the Panthers," he wheezes, "and now here I am 25 years on and I'm still talking about them."
Van Peebles has his own connections with the party. Although he was never a member, he found himself adopted as a sort of guru to the young Panthers. After directing Watermelon Man in 1970, he turned his back on a three- picture deal at Columbia to pursue his dream of giving black America an authentic voice unfettered by commercial demands. This dream manifested itself in his best-known work, the self- financed Sweet Sweetback's Baadasssss Song, which Huey Newton declared mandatory viewing for all Panthers. It was one of the first films to reflect the frustrations and ambitions of African-Americans, and as such proved anathema to white authority. How much did Sweetback alter the role of blacks in cinema?
"My film changed everything," he says simply. "After that, they suddenly started using minorities in films. That's why Spike Lee calls me the godfather of black cinema. His freedom is what I fought for. So it's more than satisfying to see him and everyone else working. It's sensational."
Presumably, he would include his son among that "everyone else". Mario made his name as a director with New Jack City, one of the flagship features of the insurgency in black cinema which opened the Nineties. But his work has never been as assured as it is on Panther. He's just as confident in person, an enormous fellow with muscles jostling beneath his vest, and soft, blurred eyes that fix on you and don't shift.
Like his father, one of the reasons he entered the film industry was because cinema was not reflecting any sort of life he had known. The release of New Jack City coincided with a number of other movies - Boyz N the Hood, Jungle Fever - which all portrayed black America with unprecedented frankness. Was it exciting to be part of this so-called new wave?
"I was certainly proud," he admits cautiously, "because at least we weren't making Home Alone movies. But on the other hand, we were all looked upon as one big cinematic basketball team, which is ludicrous. We're still at the point where we're producing `race films'. If a Rob Reiner picture flops, it's not declared the end of white cinema. If Spike's movie or mine fall flat, people say: `Everyone's tired of black films.' At least if Michael Jordan doesn't score, nobody goes `Bam! Black guys are out of basketball!' But I'm put in the position of being ambassador to the rest of our people."
He gives a baffled shrug. "I really shouldn't be an ambassador to anything other than my own strange point of view."
Does that mean you feel you're viewed as a black director rather than a director who is black?
"Absolutely. I get asked about everything from Eddie Murphy to OJ. Why don't they ask me about Joan Crawford or Talking Heads?"
It's frustrating to spend so little time with a man who clearly has so much to say. While his father speaks with a measured drawl, Mario's conversation zigzags all over the place. First he's elaborating on Panther's suggestion that the FBI allowed drugs into ghettoes to destroy them. By the time a PR assistant appears, Mario is chastising Quentin Tarantino for his appropriation of street vernacular, and come what may, he's going to finish before I leave the room.
"Tarantino stands there telling Sam Jackson, `this is not the dead nigger storage' or whatever. Now you know that there is no way ever in his life Tarantino would say that to someone who looks like Samuel Jackson. No way! He's just thinking, `I can finally say nigger to a black person - I must be cool.'"
I smile. The PR assistant smiles. Mario smiles. The look we exchange says: You can't argue with that.
n Adam Mars-Jones reviews `Panther' overleaf