Stereo speakers built like a Japanese screen surround the director, balancing his staccato tones with soothing eddies of New Age sound. Black leather couches reflect the night which looms beyond his huge windows. And four stories below us glow the night-blooming neons of Sunset Strip.

Like the TV and film work it has spawned (Miami Vice, Crime Story, Manhunter), Michael Mann Productions is a sleek and minimal complex. Yet it is hardly a place where style overpowers substance. Shelves are lined with serious reading (botany, anthropology, history) and state-of-the-art computers zing beneath a snapshot of "Mike's Chili House". Someone shuts Mann's office door, and he hunkers down even further, thinking aloud on electronic culture, on how it has changed our modes of perception, and how this defines what a Mann must do. TV with content, he insists, makes the kind of impact "people can't even really imagine."

Mann knows what he's talking about. As early as 1974, his award-winning The Jericho Mile brought made-for-TV movies a much-needed respectability. Ten years later, with Miami Vice, he changed the pace and aesthetic of advertising as well as TV. His Crime Story married the mythos of good versus evil to a classic fetish: cops and criminals viewed as each other's döppelgangers. From Brian de Palma's Untouchables through Billy Bathgate and this year's Deep Cover, that Mann epiphany carries on in American film.

Then there was Drug Wars: The Camarena Story. Made in 1990, this three-part, six-hour docudrama brought the story of "Kiki" Camarena to primetime television. A US anti-drug agent, Camarena was kidnapped and murdered by Mexican gangsters in 1985. Explicit about government links at every level of that tragedy, Camarena caused uproar from Washington to Cartagena. Mexico alone spent two million dollars demanding the White House apologise - but Mann resisted, and his program won six Grammy Awards.

During the making of Camarena, however, Michael Mann felt restless. So he went back to a project he had started in 1988: a new movie based on James Fenimore Cooper's The Last of the Mohicans. Under the aegis of 20th Century Fox, it was shot last spring. Now, Mann is editing what will be his first feature film since 1986.

That was the year he made Manhunter, a cool, inventive adaptation of Thomas Harris' novel "Red Dragon". Manhunter served as the blueprint for this year's much bloodier, Oscar-laden Silence of the Lambs (another adaptation of a Harris book with the same villain). It was Mann's idea to cast a Briton (Brian Cox) as the charming psychotic - giving the cue to hire Anthony Hopkins six years later. Even Lambs' second bad guy, a skinner-of-women called "Buffalo Bill", offers an offbeat tribute to Mann; he was played by Ted Levine, a lynchpin actor on Crime Story.

Michael Mann has always been both subversive and influential. He moves from TV to film (and back) with unusual nonchalance. Before Manhunter, he had made two movies: Thief, which won only critical raves, and The Keep, a quickly-buried failure. Mann is also something of a modern-day Roger Corman - he remains committed to the use of new and unusual talents. Many names on whom he has gambled are now famous for work of their own: especially directors such as Abel Ferrara (The King of New York), Gary Sinise (Of Mice and Men), Bill Duke (Deep Cover) and Thomas Carter (Midnight Caller).

Such creative use of risk extends to Mann's casting - he has employed as actors such celebrities as Lee Iacocca and G. Gordon Liddy. Mann has also used real detectives (cop Dennis Farina left his job for the lead in Crime Story) and real-life musical legends (Miles Davis, James Brown, Little Richard, Iggy Pop). Black and Latino actors feel that, unlike most Hollywood product, Mann's work admits there is difference between Puerto Ricans and Mexicans, Afro-Americans and Jamaicans.

The $24 million Mohicans - set in 1757 - continues all these traditions. (A main role, for instance, is taken by Russell Means, real-life leader of the American Indian Movement.) But the spark behind Mann's project came from a childhood memory. "The 1936 version was the first film I remember seeing. I recalled the lovers' end as very, very poignant." His blue eyes glitter. "It's sort of like when you remember the prepubescent erotic appeal of Tinkerbell."

Cooper's novel focuses on America's first frontier war; it is famous for creating that culture's first existential hero. What attracted Michael Mann was its combination of action, reportage and romance. "The whole thing happens in two weeks - two weeks totally packed with conflict. Thrilling history, something like the spring of 1968. France and England are fighting what was really the first World War, and each nation is allied to a different native American tribe. Plus, after 150 years of white immigration, the Indians decide their deal with the white man has reached critical mass."

He swivels in his black leather armchair. "Right in the middle, stands this guy who's a total synthesis: half working-class immigrant and half native American. Fenimore Cooper's character Hawkeye - who becomes the model American frontier hero." In this role, that of a European raised as an Indian, Mann cast Oscar-winning Briton Daniel Day-Lewis. The movie pivots on Hawkeye's "cross-cultural" love for a Scotswoman: a headstrong affair which reflects both radical times and radical change.

Day-Lewis himself has arrived in Hollywood only yesterday. Shorn of his foot-long Mohican locks, he is now months removed from the gruelling North Carolina shoot. Yet he's keen to stress the reasons he admires Mann. "The guy is such an optimist! From the point-of-view of having hung off several mountains with him, I can assure you that Michael is committed to a constructive viewpoint. He is very, very strong about the things in which he believes."

What sort of beliefs does Day-Lewis mean? Basic stuff, really: family, community, quality work. (Mann has four daughters, one a nascent film-maker, one a photographer). This director thinks that every choice one makes entails responsibilities; he believes America's true strengths flow from her ethnic diversity. Of course, Mann also thinks TV sitcoms cause crime. "Because the people they show just have so much stuff! Janitors with two-story houses, expensive cars, and Cuisinarts. If you can't get all that yourself, it's bound to make you feel substandard."

When it comes to film, however, Mann's chief belief is a simple one - absolutely everything counts. Day-Lewis puts it this way: "Michael's very, very conscious of how every aspect of film contributes; the colour, the sound, the lighting, the clothes. I never saw him once make an arbitrary decision. On a film of this scale, that takes incredible concentration."

Told about this praise, Mann laughs. Organisation, he says, is a side effect of his personal history. His college years were spent at the University of Wisconsin - one of America's trio of great '60s radical campuses (the others were Berkeley and Columbia). After university, he attended London Film School and spent several years trying to crack British film. Frustrated in those efforts, he headed for Hollywood. There. in 1975, Mann became a TV script-writer.

"That was my real beginning," he says. "Writing for TV was a workout: fast, intense, highly-structured. It teaches you about order and discipline. And it's very helpful for eliminating self-consciousness."

Self-consciousness hardly seems to be a problem for Michael Mann. But curiosity, on the other hand, gives him little rest. Mann is fascinated - obsessed - by everything from today's pop chart to progress in police forensics. He's more like a hard-boiled journalist than a Hollywood style-maker. Over the years, he's thus become an expert in various hidden histories: Mafia trails, narcotics networks, crime-fighting war-stories.

Mann gets this stuff from real people. Thief was based on tenacious months of hanging around Chicago criminals (four thieves ended up playing roles in the film). The crime-control centres seen in Manhunter are FBI labs. (In fact, their proprietors liked Mann so much, the FBI fought the CIA over attempts to block Camarena.) Mann mixes with cops and plain folk as easily as with stars; his screen world may be stylised, but the guy who creates it is down-to-earth.

Yet he admits the heady nature of wielding media power. "It first hit me one Tuesday night in 1976, when an hour-long Police Story I had written aired. The next morning I walk into 7-11 to buy cigarettes. And I hear the guy behind the counter using this phrase which I had invented! A phrase that had been on TV less than 24 hours before!"

He leans forward intently. "People's response to TV and film is a very multiplex phenomenon. So if you neglect any part of film, you're neglecting part of what is possible. It's really wild, but every part of any film is active. A sound here will change your sense of a shape which appears seconds later."

Mann's marriage of music, casting and colour schemes is legendary. In 1981, on Thief, he choreographed a night-time robbery to music by Tangerine Dream. His racy, stylish Miami Vice produced the slogan "designer TV." But the best example of tour-de-force Mann remains the finale of Manhunter: in which a serial killer pursues a blind girl through his flamboyant home - for the eighteen-minute duration of Iron Butterfly's "Inna-Gadda-da-Vida".

Mann says that film was his biggest challenge to date. "Because I didn't want to ever show the actual crimes. Instead, I wanted people gasping, "Oh, my God, I know that man!" As ever, his answer was found through inspired casting and cinematography. Tall, albino actor Tom Noonan became, like Frankenstein's monster, an eerily sympathetic killer. And the final sequence was shot without a single right angle. "Everything you see is off-kilter, everything is acute."

Mann's aesthetic has always fuelled debates about storytelling. Many critics think his dynamic imagery usurps dialogue. Others feel Mann has "modernist cool", or that he invented "high-tech TV". Few of either persuasion, however, seem to notice his actual themes: which can range from critiques of middle-class drug consumption to ruminating on the tie between between money and machismo.

Mann likes his politics as hot and controversial as his mise-en-scene. And the Columbus Quincentenary offers perfect timing for his Last of the Mohicans. What better moment could there be to challenge frontier cliché - and produce a new portrait of the First American Hero?

Daniel Day-Lewis loves the idea. He relishes the difference between his Hawkeye and John Wayne or Sam Shepard. "This was the moment," he says, "just before land-hunger. Just before the pushing-inward of native tribes had really begun. This was a time when, just for a moment, people knew how to live with each other. They knew the human politics of it, the day-to-day language of coexistence"

He glances at a production still, a picture of Hawkeye standing with his Indian brother Uncas. "The 'frontier hero'," he says, "has always been thought of as an existential loner, some guy who lives just to exert himself in war. But the real roots of that warrior image are profoundly different. The native American warrior used his strength to serve his family, his tribe and the life of his nation."

As Vice alumnus Don Johnson puts it, "Michael Mann is a heavyweight, a serious populist artist." Adds black director Bill Duke, who helmed this year's hit Deep Cover, "He's one of the most brilliant innovators the media's seen. Ever. And he's courageous: he takes on heavy issues. Sure, he may have put some of those forward in a pop format. But, in order to do that, you've got to care in the first place."

Mann's contradictory qualities - endless obsession with detail balanced by love for immersion in the moment - can produce, on film, the perfect modern marriage. But, adds Daniel Day-Lewis, there is an equally central factor which makes Mann unique. "Michael isn't threatened at all by other people's imaginations. In fact, it gives him pleasure to see where their ideas differ from his." Day-Lewis' raises one dark eyebrow. "In this business, I don't have to tell you how rare that is."

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