Mariah Carey is about to enter the room. At least that's what her people are telling me. I'm sceptical because they have been telling me the same thing in slightly different ways for the past three hours. Now here I am, in a chintzy hotel suite at the Dorchester at 9.30 on a Friday night, and my initial anger has given way to a sort of weary resignation, because to be invited into the world of Mariah Carey one has to leave normality far behind. This, after all, is the global megastar who, if the media reports are to be believed, once insisted she "didn't do stairs" and whose backstage demands are said to include baskets of puppies and a special attendant to dispose of her chewing gum. The time delay, it seems, is all part of the sensory experience.
Still, the signs look hopeful. At around 9.40pm there is a sudden flurry of activity in the hotel suite as several smartly dressed women walk in, cast their eye over the room and walk out again. One of them shrieks with horror when she notices that a corner of the rug has been disturbed and rushes over to flatten it with her hand. Another one places a bottle of mineral water on the table in front of the sofa. "Will she need a straw?" the woman asks. "I would anticipate the need for a straw," replies the bodyguard gravely, as if he were a top-level physicist working overtime to ensure the smooth operation of the Hadron Collider.
Then, miraculously, everyone disappears as though they have been sucked away by the tidal drawback that heralds a tsunami, and Mariah Carey walks in. Actually it is more of a teeter she is wearing knee-high black boots with a 6-inch heel and seems to be having difficulty negotiating the plush white carpet. She wobbles over to the sofa, a glass of red wine held perilously askew in one hand, and lowers herself down in stages until she is sitting precariously on an overplumped cushion. "Actually the chaise would always be my favourite," she says, gesturing vaguely towards a chaise longue in the corner of the room. A lackey instantly offers to move it for her. "No," says Carey, smiling like a benign feudal overlord, "I won't go that far." Instead she hoists her legs onto the sofa and reclines backwards, the heels of her boots catching slightly against the upholstery as she does so.
At 39 she makes quite a visual impact: tumbling golden-brown hair, honey-toned skin and a formidable cleavage that is today enhanced by a necklace with Carey's stage name Mimi spelled out in diamonds. Her face is pretty but unthreatening, bronzed and buffed with layers of perfectly applied make-up. Unlike many celebrities, Carey looks exactly as she does in her promotional photographs, as though the airbrushing somehow seeps through into real life. Everything about her is unapologetically overdone, a caricature of fabulousness. "This height of heel is what I wear," she explains at one point. "Even my slippers. I can't even walk in flats."
Fortunately her difficulties with perambulation have not held her back from becoming one of the biggest-selling singers of all time. Over a career spanning two decades, Carey has sold more than 160m albums worldwide and has had 18 number ones in America, surpassing both the Beatles and Elvis Presley. She has won five Grammys and has just released her 12th studio album, Memoirs of an Imperfect Angel. Her voice is believed to span five octaves and many of her hits We Belong Together, Hero, Without You are covered by X Factor contestants desperate to show off their vocal range.
But it is as an actress that Carey has recently been gaining considerable critical acclaim. Her role as a downtrodden social worker in the forthcoming Precious, directed by Lee Daniels, who produced the Oscar-winning Monster's Ball in 2002, has been hailed as "pitch-perfect" by Variety magazine and earned her a Breakthrough Performance Award at the Palm Springs International Film Festival.
Precious, which tells the harrowing story of an overweight and illiterate teenager who is abused by her mother and is pregnant for the second time with her father's child, caused a sensation in the States, where it took $1.8m on its opening weekend despite its challenging subject matter. The film, which opens here on 29 January, is based on the novel Push by the American street poet Sapphire and has an almost entirely black cast, as well as being backed by some of the most powerful names in entertainment, including Oprah Winfrey, the executive producer, and Lenny Kravitz, who plays a maternity nurse.
Carey was not, it must be said, an obvious choice for the role. For years her acting career had struggled to emerge from the monstrous shadow cast by Glitter, the 2001 semi-autobiographical movie that was panned by critics, many of whom called it the worst movie of all time. The Village Voice reviewer wrote that when Carey tried to show emotion "she looks as if she's lost her car keys".
"I think Lee takes chances with people he feels are artists," Carey admits. "Yeah, I think he had a lot of guts to do that, because people have really, really trashed me as an actress."
Daniels, who had previously worked with Carey on the 2008 film Tennessee, says that when he told the crew he had cast her "they looked at me like I was nuts… but I know Mariah's work I think she's a formidable actor. The irony here is that the Glitter experience hurt her more than anyone because she's such a perfectionist. I just find her work ethic extraordinary. When she came on set, she kicked right into gear because she didn't have a posse; she was part of it. Mariah didn't even have a dressing room. She had a room that was the size of a public bathroom to change in."
In Precious Carey plays Miss Weiss, a world-weary welfare officer who gradually unpicks the heroine's horrific life story. Helen Mirren was originally slated for the part but had to pull out at the last minute because of scheduling commitments. Daniels called Carey up two days before they were due to start shooting. Luckily she had already read the book twice and threw herself into the preparation.
"I spent as much time as I could getting into it," Carey says. "She is supposed to be exhausted, so it didn't matter that I stayed up … I really did the best I could to morph into this woman who goes into this office every day and deals with people needing something from her, trying to get things from her, maybe being disingenuous."
The end result is a revelation. Carey's performance is heartfelt and totally stripped back in many ways the very antithesis of her puffed-up public persona, with its emphasis on outward appearance and conspicuous consumption. Daniels insisted that Carey wear no make-up and refused to allow her notorious entourage on set. Carey had to readjust her voice, her posture and her walk. "Mariah was born as an embryo in stiletto heels," says Daniels. "She walks even in her home on her fucking toenails! I said: 'This woman is not going to work if you're walking like Princess Tippy Toes.'"
Carey is gracious enough to laugh about it now. "He put a moustache on me," she says matter of factly. "He put red stuff under my eyes. He made me have like almost a unibrow. The hair I mean, the hair! and the clothing wasn't exactly my style, but it didn't matter. I was there."
For someone so accustomed to being primped and preened for videos and television appearances, I wonder whether the experience of playing Miss Weiss was liberating. She approaches the question indirectly. "I am very insecure about my looks, and I always have been because of being mixed race [Carey's mother is Irish-American and her father was an African-American of Venezuelan descent]. It's not so weird now, and everyone's accepting it in a big way, but as a child I felt very, um, out of place and didn't feel pretty. So taking on that character and having Lee make me older in the way he did, I guess it was freeing because I didn't have to try in any way to look pretty, and you know, when you grow up with that type of insecurity you don't always feel pretty." It is an unexpectedly raw answer. Does she feel pretty now? "Sometimes I feel all right."
Part of this discomfort is a legacy of her upbringing her mother's parents disagreed with interracial relationships and disowned their daughter when the couple got married. Carey's parents Patricia, an opera singer, and Alfred, an aeronautical engineer who died in 2002 divorced when she was three. Her mother struggled to make ends meet by singing in jazz and folk clubs and the family moved around a lot. Carey's older sister Alison had her first baby when she was 15 and became a prostitute. She is now HIV-positive. For legal reasons, Carey cannot talk about Alison, but it is clear that those experiences have left their mark.
"I don't want to go into my family stuff, but there were very difficult things that took place," she says. Later Carey adds: "I think certain people like to torture me because they think I've had it easier than I actually have and they think: 'Oh, she's got this, she's got that, she's always had everything perfect' and it's sooo not true. You know, I really relate to this movie in a lot of ways."
She frequently experienced racism growing up as a bi-racial (this is her word) child in Long Island. Neighbours allegedly poisoned the family dog and set fire to their car, and she says, when I ask, that the first time she realised she was different was aged six, when she took her white best friend on one of her weekly visits to see her father.
"She got out of the car and went up the stairs to his house and he was over 6ft tall and very handsome, but to her he must have really been scary because I don't know that she'd ever seen a black man before. And she looked at him, her mouth went open and she started screaming and crying.
"I think he was trying to make me feel better and calm her down, but it didn't work," she pauses. "You never know what people say in their houses about different races. So my mother took her home and I went up the stairs with my father."
Carey's sense of identity was further confused by her early commercial success. In 1988 she met the president of Columbia Records, Tommy Mottola, at a party and gave him her demo tape. Mottola signed her up and set about packaging his new protégée as the pretty girl-next-door singing bubblegum pop for a predominantly white audience. The two of them later became romantically involved and married in a lavish ceremony in 1993 when Mottola was 44 and Carey was 23. She has subsequently described Mottola as "controlling" and the four-year marriage as "stifling", but her career took off in spectacular style and she had a number one single in every year of the 1990s. It was only when they divorced in 1998 that Carey began to flex her own creative muscles: her songs became more heavily influenced by hip-hop and her image more overtly sexualised.
Did Carey feel the way that she was packaged by Mottola deliberately ignored her cultural heritage? "Usually the black community knew that I was black, but white people didn't always they hadn't always experienced being around people who were half-black, half-white and who looked more white. My mum's very, very Irish and my father was light-skinned, so I turned out the way I turned out."
Does she still experience racism? "Yes. It'll be a mild thing that I'll get over, but a friend said to me the other day: 'Oh yeah, you'll like her –she's like you, she's got a black husband' [Carey married the 28-year-old actor Nick Cannon last year]. And I'm like: 'How many times do I have to tell you my father was black. My mother's white. In this country that makes you black, do you understand? I know I'm very light-skinned, but stop doing that!' It's one of those things that the world doesn't quite understand. When I first came to Europe, everybody was asking me: 'Why do you always have black people in your music videos?' And I was like, errm, how do I answer this one?"
Perhaps Carey's need for success is driven by her need for acceptance in much the same way as her desire for total control stems from a fear of what happens when you are denied power over your own life. Hence the demands for chaise longues and drinking straws and chewing-gum disposal operatives: if Carey can stage-manage every tiny detail of her environment, she is protected. Lee Daniels says that Carey is "one of the smartest girls I know. She detects bullshit. She detects non-talent, and that's when she takes control… Sometimes she's wrong, but because she's right so often she digs her heels in and it's impossible to communicate with her."
Does she need to be in control? "I can be thought of as a control freak," Carey admits. "Trust is always an issue for me. It's never been easy for me to trust anybody, and that's kind of a sad thing to say, but it's true."
The control freakery imploded spectacularly in 2001 when Carey suffered a very public breakdown. Glitter had just been released to awful reviews and Virgin, the record label she signed with for $80m after splitting from Mottola, had dropped her. Carey started claiming that Marilyn Monroe was speaking to her through her piano and leaving incoherent messages on her website. After collapsing on her mother's kitchen floor, she was hospitalised for nervous exhaustion.
Carey says now that the breakdown was a result of overwork she regularly puts in 14-hour days (presumably factoring in time delays) but that, if anything, it left her even more determined to succeed. She later signed a contract with Island Records, and in 2005 The Emancipation of Mimi became the best-selling album in America. "I'm proud of having enough faith to always get up and try again," Carey says. "And just being strong enough to get through stuff."
What with the album sales, the acting career and the inevitable launch of her own-brand perfume, Carey is now thought to be worth around $225m and is ranked as the sixth richest woman in entertainment by Forbes magazine. However ditzy Carey might appear, beneath it all beats the heart of a savvy businesswoman it is hard not to conclude that her diva-ish antics are simply part of the package that her fans buy into. Part of me would have been disappointed if Carey hadn't made me wait for three hours, and she is astute enough to realise this.
But in person she is far more considered, intelligent and warm than her image would have you believe. As I leave, Carey is already having her hair and make-up retouched by a bevy of helpers. The suite has several doors and I am not sure which one leads out into the corridor. No one tells me where to go because they are all too busy plugging in hair curlers and locating drinking straws. It is Carey who spots my confusion and opens one of the doors, ushering me outside with a kind smile. Mariah Carey might not do stairs, but I can exclusively reveal that, yes, she is capable of opening doors.