When the film director Ridley Scott was making Gladiator, he hired Kathleen Coleman, head of classics at Harvard, as the film’s official historical consultant. During the production her advice was ignored and, eventually, “deeply disillusioned by the final product, which makes virtually no attempt to represent an authentic Roman past” (as she put it on a website for classicists), she asked for her name to be taken off the credits.

Coleman was appalled by Hollywood methods. One message from the production office said: “Kathy, we need to get a piece of evidence which proves that women gladiators had sharpened razor blades attached to their nipples. Could you have it by lunchtime?”

In a recent book about Gladiator, she wrote an essay called “The Pedant Goes to Hollywood”, in which she noted that “scholars are, of course, notorious for being obsessed with detail - but detail is the repository of authenticity.”

Gladiator, released in 2000, grossed $457m worldwide and created a spectacular revival in the Roman epic genre - one that had been around since the beginning of cinema. The first filmed version of Ben-Hur was shot at a New York beach in 1907. Like most early Roman epics, it drew its story and look from the neo-classical movement: novels and plays, and paintings by the likes of Lawrence Alma-Tadema.

In his book The Phantom Empire, Geoffrey O’Brien explains how, as the film industry developed, Italian and American directors influenced each other to create what became the standard, mythical view of the period: “It was,” he writes, “as close as movies got to a cultural lineage, this process of spirals within spirals by which you got the myth (the real, original Italian epics, Cabiria and Quo Vadis and The Fall of Troy, that took America by storm in 1914) and the myth of the myth (the improved and homogenised American epics, Intolerance and Ben-Hur and The Queen of Sheba, which in turn found their way back to Italian screens) and then, beyond computing, the myths of the myths of the myths, as each photographed the others’ photographs.”

Across the genre, down the decades, the look for temples, togas and centurions became standardised. In the late 1950s, cheap “peplums” (a derisive term from the Latin for a ruffle attached to the waist of a tunic) cheerfully recycled the same sets, props and actors in film after film, sometimes even using the same shots. But the epics overreached themselves - and were all but killed off in the early 1960s, by the excesses of Cleopatra and The Fall of the Roman Empire (whose Forum, built outside Madrid, was four times the size of the original in Rome).

Gladiator’s success changed all that, and now it feels as if the epics have never been away - though the failure of Troy, and the potentially larger failure of Alexander, may produce another climate change soon. For the moment, though, they and all other recent film representations of antiquity stand in Ridley Scott’s shadow. Yet, as Coleman’s anger reveals, the most interesting aspect of Gladiator may prove to be - when it is itself ancient history - the dispute surrounding its lack of historical authenticity.

Scott is a brilliant visual stylist, and his film is a masterpiece, but he played fast and loose with history, trumping previous versions of the tale by wielding myths-of-myths-of-myths with much the same panache as his gladiator hero Maximus used a sword. The key sources were not ancient Roman texts but more modern fantasies. He first had the idea for the film when he saw a picture painted in 1872 by the French artist Jean-Leon Gerome. The picture, “Pollice Verso” (Thumbs Down), shows a gladiator in the arena standing with his foot on the throat of a rival as the crowd urges him to kill. For his story, Scott drew heavily on The Fall of The Roman Empire, Spartacus and Ben-Hur. Most controversially, for the scene in which his tyrannical emperor Commodus enters Rome, Scott used a shot-for-shot pastiche of Leni Riefenstahl’s Nazi epic Triumph of the Will. When critics accused Scott of flirting with fascistic imagery himself, he responded that the Nazis had copied the Romans, “so you’ve got it the wrong way round”.

His cyber-generated Rome was also mostly pastiche, assembled from architectural photographs of neo-classical buildings in London, Maltese churches, a Napoleonic-era fort and other sources. When he was told that ancient Romans probably never had pavement cafes, Scott filmed a cafe scene anyway and declared: “This is the first coffee bar in Roman history.” In his commentary to the DVD of the film, he took issue even with the historical experts who had supported his film, the ones who said Gladiator had taken a few liberties but generally looked pretty good. “I’d say, ‘How do you know? You weren’t there.’ What we do is jump back in time into our own imaginations, and that is the most important thing to do. Historians say, ‘I’m not sure that they did that.’ And we say, ‘Well, they bloody well do now.’”

Close your eyes and picture ancient Rome. What do you see? Eagles, gladiators and white togas, no doubt. Hillsides covered with classical, ivory-coloured temples too, probably. Straight lines. Huge crowds. Forests of gleaming white marble columns and statues. A place glowing with what Olivier in Spartacus called “the might, the majesty, the terror of Rome”.

That’s the classic Hollywood view. Rome the pale, the pristine, the venerable is an image as old as film itself. And because we get our view of Rome primarily from the movies, the myth lies at the core of our sense of antiquity, of our sense of history, perhaps even of ourselves.

But what if it’s all completely wrong? At modern Rome’s fabled Cinecitta studios, the BBC and American TV giant HBO have joined forces to shoot an epic $100m television drama series that aims to topple the Hollywood image and set a new vision in its place.

Simply called Rome, the painstakingly researched show is shaping up as a vast, operatic, Grand Guignol drama. Its epic story will weave the lives of two ordinary Roman foot soldiers with historical celebrities such as Julius Caesar and Pompey in the last years of the Roman Republic. The show’s relatively unknown British stars - Kevin McKidd, Ciaran Hinds and Polly Walker - are likely to become household names.

In keeping with ancient Hollywood traditions, Rome will feature intrigue, spectacle and casual brutality. In a radical break with Hollywood traditions, though, it will also be jammed with cliche-busting surprises. There’ll be much more sex and paganism than we’re used to. We’ll see Julius Caesar as he really looked during his ceremonial triumphs (painted head to toe in Jupiter’s colour, red) and Cleopatra will not be a vamp or demi-goddess, but as Cicero saw her - a dinner-party bore.

HBO is putting up most of the money. The first 12 episodes are due to air late this year, and if all goes well a further four seasons are planned. So far, though, the show’s most spectacular feature is its jaw-dropping set, reckoned to be the biggest and most expensive ever built for television. On the backlot at Cinecitta, where Ben-Hur’s chariot race was filmed and where 500 slaves once dragged Liz Taylor into town atop a giant sphinx for Cleopatra, a spectacular new version of the ancient city has been built of steel and fibreglass. There’s a full-scale replica of the Forum, a warren of working-class streets, markets, villas and gardens.

It looks tremendous, but also weird, because this Rome is grubby rather than grandiose. Its temples don’t shimmer but are dirty and multicoloured. The set is smoky and covered with Latin graffiti, much of it obscene. On street corners there are candle-strewn shrines and drawings of giant penises. In one street there’s a typical Roman toilet: a latrine with planks with holes where men and women sit side by side and use the same fetid sponge as toilet paper. Grass grows between the flagstones on the Via Sacra. There’s mud everywhere.

Welcome to the new, realist, “authentic” Rome: feral, vivid, jumbled, irregular. “Third world Rome”, the show’s executives call it - a bracing, provocative antidote to a century of “Hollyrome”.

Production designer Joseph Bennett, who built the set, says: “People think of Rome as white and cold and beautiful, powerful but distant. But based on the research, I don’t think it was like that at all. If you go to Pompeii, you’re struck by how garish it is, even now. The temples and sculptures were all brightly painted. Rome was like Pompeii, but much bigger. And Rome was so noisy it was impossible to sleep. It was like hell. Think of it as a combination of New York and Calcutta, with insane wealth and insane poverty. It was pretty extreme.”

”We’ve taken everything from scratch,” says chief writer and executive producer Bruno Heller. “We are disregarding what people might have seen before, and asking: what was it actually like at this moment in history? We’re trying to deal with the lives of ordinary people, the details of routine, everyday life, of unemployment, of disease. And we are trying to be very precise in the historical moment, very precise about the texture of everyday life. Everything flows from that. The Forum was about as grand as it got, but it was not, by any means, stupendous or stupefying. Once you know that the Tiber flooded regularly and the houses were constantly on fire because they were just made of wood, you know that there were fires and floods constantly. It was always smoky, grimy and dirty.”

Every aspect of Rome’s scripts and production are backed up by detailed research, and historical consultant Jonathan Stamp is a key figure behind the scenes. As Jane Tranter, the BBC’s controller of drama commissioning, puts it: “Gladiator was marvellous entertainment, but we at the BBC are not going to give a huge amount of money to recreate a period of history and make something that is not based on any kind of truth. People want to unravel and discover things. And we want to be able to offer them that extra frisson of: ‘You know what? It all happened.’”

The production comes at a time that future generations may one day classify as a crucial juncture in western history. For the first time in hundreds of years, the west is losing direct contact with what it once considered its roots: with the “classics”, with Rome. Once a staple of academic life, ancient Greek has all but disappeared from schools, and Latin is heading the same way. Despite a slight revival following the popularity of Gladiator, ever fewer schools and universities teach the subject. And it’s not just happening in Britain. Direct knowledge of the texts and language of the classical past has sharply declined throughout Europe and America since the 1960s.

What we are left with is popular culture’s view of Rome. We have ancient Roman computer games (Rome: Total War, Gladiator - Sword of Vengeance), ancient Roman popular historical fiction and crime thrillers (Eagle in the Snow: General Maximus and Rome’s Last Stand; One Virgin Too Many). And, above all, we have the Roman fictions of the screen, a form so potent that Coleman says: “The Rome Hollywood created is now the only Rome that is universally familiar.”

If Hollywood’s Rome is wildly wrong, we might even be in trouble. “If you know nothing about Roman history you begin as if memory began this morning,” Stamp says. You can’t function morally if you don’t have a memory. You can’t function at all. The past is our collective memory. Without it we’re screwed.”

Imperial Britain, revolutionary France, the early US and the Nazis (among many others) all imagined themselves to represent a “new Rome”. For the neo-classicists of the 18th and 19th century, Rome meant nobility, wisdom, self-sacrifice, civic virtue and moral purity. Rome was the model to which the founding fathers of the US aspired: it was above them and would raise them up. America’s public buildings have columns, pediments and domes because they were modelled on the clean lines and assumed whiteness of Roman temples and the Pantheon.

By contrast, Hitler believed that “all that remained to remind men of the great epochs of history was their monumental architecture”. He ordered architect Albert Speer to create monumental Nazi structures that would look as good thousands of years after they were destroyed; as good as Roman ruins did. If he had won the war, Hitler planned to raze Berlin and build in its place a new, crushingly vast capital city consisting mainly of huge Roman-style buildings, some of them hundreds of times bigger than the originals.

Modern, imperial, consumerist America created yet another vision. Hollywood’s view of Rome as an empire of sex, sin and infinite consumption found architectural expression at Caesars Palace, Las Vegas. Certainly, it resembles no building ever produced in antiquity, but its vertiginous white marble towers, gold-topped columns and pediments, talking statues and opulent fountains faithfully reflect the spirit of Cleopatra. Jay Sarno, the flamboyant businessman who built the resort with a loan from the Teamsters’ pension fund, wanted to create a world of fantasy “fit for an emperor”, where every guest would feel like a Caesar or a Cleopatra. When the joint opened in 1966, its cocktail waitresses wore skimpy togas, there were chariot rides, pretty “slave girls for the personal needs” of important guests and, in the Circus Maximus theatre, Andy Williams performed a show called Rome Swings.

In a sense, each of these architectural fantasies was as plausible as the other. Each took an element of authentic, historical Rome and stretched it to distortion.

Diverse interpretations have flourished not only because Rome is the single most important culture in the development of Western civilisation, but also because the myth of Rome is uniquely flexible. Jonathan Stamp argues: “The best, most powerful myths are the ones that can stand for different things at different times. Rome remains our top-dog myth because it stood for completely different things. You can’t say the same thing about the Greeks. They were always eggheads no matter how you cut it.”

Stamp suggests that we see Rome as being split between its austere Republican phase and its opulent imperial period. “The republic stands for self-denial, closeness to the land, parsimony, asceticism.” At the other end of the spectrum, the legends of crazed, sensualist emperors spawned the porno Rome vision of a movie like Bob Guccione’s Caligula. And cinema has become the most potent purveyor of myth ever invented.

But do audiences care if filmed history is authentic? The legendary Las Vegas art critic Dave Hickey, who sees the themed casino resorts in his city as physical incarnations of Hollywood myths, thinks not. “It’s the illusion of authenticity that people like. They want things to feel authentic, but they really don’t care about the details.” He cites the case of the Luxor, the Ancient Egypt-style resort in Vegas that features exotic-looking Egyptian-style hieroglyphs. The feature attracted interest and the designer went on TV. “Hey, this isn’t just decoration,” he said. “These are real words. This stuff means stuff!”

An axiom of the BBC-HBO show is that its stuff means a lot more than stuff. Its stuff is, in fact, part of the essence of the project. The attention to detail on set is impressive. When the script called for thousands of gold coins stamped with Caesar’s head, props master Arthur Wicks (with the aid of “a little man in the Vatican”) made thousands of replica gold coins stamped with the head of Ciaran Hinds, the actor playing Caesar. The show’s superb costumes, made by April Ferry, are not the traditional Hollyrome gauzy white or pastel style based on Alma-Tadema’s paintings, but rougher, heavier, redder, and made only from materials the Romans would have used - wool, silk and cotton.

The desire for authentic detail has yielded some startling insights. Unlike Hollywood’s Roman-Christian epics, Rome tries to bring alive the religions of Romans and their cultish obsessions. In episode one the main female character Atia (think Joan Collins in Dynasty, but in an authentically Roman way) visits a temple and, according to Heller’s script, “showers in blood”. Bennett considered the idea preposterous, but researched it and discovered it was indeed based on what we know of ritual. “They used to lead a bull into a special wooden frame, cut it and the animal’s blood would be used as a libation on the body. Your imagination could never come up with anything like that. The moralities were just so completely different.”

Even gladiator contests in the show won’t look the way we’re used to. “Part of authenticity is what an audience expects, but one hopes to jolt or at least challenge preconceptions,” says Bennett. In the period in which the show is set there was no Coliseum. Gladiator fights, staged in the Forum, were more like a modern travelling circus, or a bull fight, or an occasion on which criminals were dispatched by professionals in front of small crowds with nowhere better to go on an afternoon. It was bloody enough, to be sure. On one day of shooting, 11 gladiators got their heads, arms or other parts lopped off in front of a baying crowd of Italian extras. But “it was on a more human scale than we thought, and fights weren’t always to the death. You end up with something you haven’t seen before. We can’t compete with the scale of Gladiator, but hopefully this is fresher. You make your own myth.”

Heller describes the overall style of Rome as “Ben-Hur meets Kes or Cathy Come Home”. Tranter says it’s much more like “Ben-Hur meets The Sopranos, with a bit of Mean Streets thrown in.” Either way, it will deliver what Jonathan Stamp says is a “severe corrective” to Hollyrome.

How the epic scale fits with the BBC tradition of clever, low-budget takes on the period is harder to judge. The 1976 classic I, Claudius was sublimely written and acted, and seeing a tape of it six years ago was what first set HBO executive Anne Thomopoulos thinking about the idea of doing a Roman drama.

But audiences today simply would not accept the production values of I, Claudius. As its star, Derek Jacobi, says, “If you looked very carefully from scene to scene you would notice that the walls didn’t change. We just moved the potted plants around to make it look like a different location.” Meanwhile, Carry On Cleo was shot on the lavish set that Cleopatra left at the Pinewood studios when production switched to Rome. Carry On Cleo cost a tiny fraction of the epic, but ended up the more satisfying and coherent movie. Ancient Romans would have preferred it too, says Heller. “It didn’t make a song and dance about this foreign strumpet. Like Up Pompeii, it was very much in the Roman style - very broad, very vulgar, and in your face.”

Yet, inevitably, if it succeeds, Rome will itself end up creating its own myths, because all films and TV fiction about the past - and indeed all history writing to some degree - involve imagination and conjecture. The past is capable of infinite reinterpretation. The point, perhaps, is not to produce the definitive vision of Rome, but to engage with it from as informed a vantage point as possible.

Artistic visions of Rome have tended to serve the needs of the time in which they are made. The Christian evangelism of Ben-Hur, the fascist propaganda of Mussolini’s Scipio Africanus and the anti-fascism of Spartacus are all equally anachronistic in that they read Roman events backwards from the vantage point of the 20th century, something Romans themselves obviously didn’t do.

”Life on a day-to-day level is very rarely epic,” says Heller. “We know this period was a turning point in western history. But if you were living in it, it wouldn’t have appeared so.” He is determinedly trying to avoid resonances with our own time, or indeed with any other period of history. “It would be false, though of course we allow the audience to make those connections themselves, if they wish. Much better to try as far as possible to deal with the world entirely in Roman terms, in terms of what they thought was going on. They had no sense that the Republic was coming to an end. When Brutus, Cassius and the rest killed Caesar they thought the Republic would just recreate itself.

”As far as possible, we stay in that time frame. It’s a contemporary drama about Romans. I’ve tried to make it a show that ancient Romans would understand and enjoy.”