Our heroine is young, wholesome and effortlessly beautiful. Tiana works hard, smiles sweetly, and flutters her eyelashes – a lot. After a series of unlikely events she ends up marrying her Prince Charming. Then, we must presume, everyone lives happily ever after. So far, so normal, in the cotton-candy nature of fairytale romance, but do not be fooled. This leading lady is tearing down cultural barriers.

Seven decades years after Walt Disney's pencil-wielding animators gave Snow White to the world, Tiana is about to debut as Hollywood studio's first ever African-American cartoon princess. The Princess and the Frog launches this week in New York and Los Angeles, before rolling out across America and at least 30 other countries, hitting the UK in late January.

To Disney, Tiana's launch is both a symbolic milestone, and a serious commercial opportunity. When The Princess and the Frog was first announced, in early 2007, she was lauded as a positive role model with the potential to reach out to black audiences, a frequently-ignored section of the film-going public, and lure them into movie theatres.

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Her "voice," the Broadway actress Anika Noni Rose, was pegged as a major star in the making. "I grew up watching Disney films, and always wanted to be in one, but I thought I'd be cast as a skunk, or something. I never guessed that I might play a princess," she recalled, when The Independent caught up with her last week. "This is something that people were so excited for, and so ready for, that it's just a dream come true, in a much grander fashion than I'd ever hoped."

The dream hasn't always run smoothly, though. Disney originally hoped that the heart-warming nature of Tiana's rags-to-riches story would broaden its social appeal and erase any lingering memories of their studio founder's flirtation with racist politics in the 1940s. But the press at times read from a different script.

After the decision to create the studio's first black princess was announced, commentators began to explore its potential implications. Plenty of them decided that it was nothing more than a cynical stunt. Many bristled at the thought of what they presumed was a largely-white production team "Disneyfying" jazz-era, 1920s New Orleans, where The Princess and the Frog is set.

Still more were upset by early revelations about the plot, which casts Tiana's mother as a servant for a wealthy family of white people, and expressed serious reservations about the profile of the film's sinister villain, Dr Facilier, who is a black voodoo magician.

A year ago, amid mounting disapproval, a highly-critical editorial article in The Voice – perhaps the Western world's most prominent black newspaper – dubbed the whole project "disappointing".

At the time, Disney could say little in response. Spokesmen counselled that people should wait until they'd seen the film before knocking it. The studio press office did, at one point, publicly rebut some wilder rumours, including one that suggested a white actress would be voicing Tiana. But the real test of their black princess would, they maintained, only come at the world's box offices.

Now, finally, that is about to happen. The first reviews of The Princess and the Frog will be published this week, and the paying public's reaction will begin to take shape once the movie hits cinemas on Wednesday. And if the all-important buzz is anything to go by, omens for the picture are pretty good.

For one thing, every showing in New York and LA for the next fortnight is already sold out. And the film has already secured some valuable endorsements from within America's black community. Leading members of the National Association for the Advancement of Coloured People were invited to a screening in LA last week – and responded with a 10-minute standing ovation.

Advanced screenings have also generated surprisingly positive feedback (over 80 per cent approval, according to studio sources). Most experts expect it to be one of the biggest two or three titles to hit American cinemas in the lucrative pre-Christmas window.

"The general consensus with this film is so far that yes, it's very good indeed," says Tim Gray, the editor of Variety. "So my prediction is that it's going to do very good business. "I'm sure there are racists in America who having a black princess will be a factor for, but I don't think they will stop this being a hit. When kids and families can fall

in love with Shrek, a green monster, or a fish, in Finding Nemo, or a robot in WALL-E, I don't think skin colour is a huge issue."

If he's right (and, in fairness, predicting box office success is always something of a crap shoot), then Disney must take credit for adopting a painstakingly careful approach to the creation of its first African-American princess. Last week, the studio explained how it had consulted with a wide range of prominent black individuals and organisations while finalising the tone and plot of the film.

This exercise saw them change the film's title (it was originally to be The Frog Princess) and also write in a bigger role for Tiana's father, so as not to advance stereotypes about black, single-parent families. The heroine's name was also altered: originally, she was to be called Madeleine, but focus groups complained that "Maddy" sounded dangerously like "Mammy," an unwelcome reminder of the segregation-era Deep South.

The film-makers also knocked on the door of black America's greatest opinion former, Oprah Winfrey. She was asked to cast an eye over the script to highlight any potentially tricky areas, and was so taken by what she saw that she requested (and got) a small role in the film, as Tiana's mother.

Oprah also suggested a small, but important plot change. Peter Del Vecho, the film's producer, revealed that she advised him that Naveen, Tiana's brown-skinned Prince Charming, should be re-inherited by his parents (he begins the film penniless) when he eventually secures his bride.

"When we realised what a big deal having a black princess was, we wanted to of course make sure that we did it right, so we consulted widely, with Ms Winfrey and others, and got lots of very helpful feedback," he recalls.

Del Vecho also crucially hired Rob Edwards as his screenwriter, who had achieved prominence writing The Fresh Prince of Bel-Air, a 1990s sitcom deemed ground-breaking because it focused on a black family from an extremely privileged and wealthy background.

The outcome of this lengthy exercise in stepping on eggshells is that the only people who could really take offence from The Princess and the Frog are white viewers, who may ironically complain about instances of inverted racism. One villain is a fat, white servant with a plummy English accent; others are white estate agents. A comic turn is performed by three red-necked inhabitants of rural Louisiana, who boast nary a tooth between them.

Away from the box office, a range of merchandise – including slippers inspired by the film's trumpet-playing alligator Louis, and themed tarot cards – is already in stores. The film also boasts a potentially-lucrative jazz-themed soundtrack. And its "look" – it is Disney's first hand-drawn animation for several years bucking the trend for computer-generated imagery – could reignite interest in the firm's back catalogue.

Marketing experts therefore say that the film's wider commercial prospects are robust. "As a practical matter, broadcasters and film studios simply have to reflect their audience," says Darren Campo, a TV executive who recently published the science fiction novel Alex Detail's Revolution, which has a black female protagonist.

"In the case of this film, I think the Disney factor is going to attract a big commercial following anyway. And the curiosity factor of a black princess, might also end up pulling in audiences who wouldn't normally go to see a Disney film."

And that would be just fine for Disney, and also for Tiana's alter ego, Ms Noni Rose. "In the history of cartoons, brown-skinned people, of many different ethnic backgrounds, have not been treated well," she reflected. "Traditionally we're the villains, we're the bad guys, we're the scary apparition coming from the back. But, with this film, that's now changed. When people see the movie, and realise that it has been made with real love and respect and care, I think their concerns will very soon disappear."

Walt's women Changing face of Disney

Snow White

The raven-haired beauty made history as the star of the first feature-length animated film ever made. Pinched from the Brothers Grimm fairy tales, her 1937 debut helped turn Walt Disney from a talented eccentric into one of the most powerful men in the history of Hollywood.

Jasmine

The first non-white Disney princess was rolled-out in the 1993 film Aladdin. But the cartoon promptly sparked protests from Muslims, and Arab nations, who said the film was racist in its depiction of a Middle East riddled by violence.

Pocahontas

A Native American princess probably seemed like a good idea at the time. But the beauty, who fell in love with a white settler in the 1995 movie, attracted stern criticism. There were complaints from the Native American community that her face had actually been modelled on Naomi Campbell.