There are a lot of people in Mariah Carey's house a grandiose mansion in a gated community in a suburb of Los Angeles. There's a camera crew, make-up people, photographers, housekeepers, a manager, assistants, bodyguards and people who carry things around. It's 10pm.
Outside it's dark and deathly quiet, inside it's buzzing with preparation for her Sweet Sweet Fantasy European tour (she plays the last of her six UK dates tomorrow in Cardiff and at the O2 in London on Wednesday). All of the prep and every aspect of Carey's life is being filmed for a documentary.
She brushes past me in a black laced-up gown and Tom Ford heels. Everyone else in the house, including her glamorous manager, seems to be wearing Louboutins. I'm told I may have to wait. So I wait in the rented house that came furnished with over-stuffed couches, mahogany twirly bits and endless chandeliers. The bathroom has black velvet walls and black diamond-patterned handtowels.
I inspect the silver-framed pictures of Carey, 45, and her four-year-old twins, Moroccan, a boy, and Monroe, a girl she is known to refer to them as "Roc'n'Roe", and they have their own fansites as "DemBabies". They're at the beach, on a boat, in the sea. They look relaxed in some other life, the opposite of this chaos. It's always just Carey and her babies. There's not a photographic hint of their father, her second husband, the actor-rapper-entrepreneur Nick Cannon, or her new fiancé, James Packer, the son of the Australian billionaire publishing magnate Kerry Packer. I say I need to leave by midnight, knowing there's little chance I will.
When I resist being filmed myself, it does not go down well. Carey says in her velvet purr: "Why don't you want to be filmed, Chrissy?" Because I want intimate, not a performance. She gets it and asks them to go away. She seems relieved, too, that she's not being scrutinised.
Why have all these people in her house? "I want people to see the whole thing. It's a busy time right now, and I happen to be on a night schedule." Indeed, communicating with her during the day has been impossible not because she is a diva, but because she was simply asleep. "I do sleep in the daytime, but not all day because of the kids, so it's a little bit sporadic. I need to sleep, and so I do. I've always been a night person. When I was six years old I wasn't able to sleep. It started then. I was up all night and that was the precedent."
I am sitting on a velvet cushion on the floor beside Carey, who is on a huge multipillowed armchair. You can imagine her as that child who couldn't sleep, who felt she didn't fit anywhere with her white Irish mother and an absent African-Venezuelan father. She was three when her parents divorced. But she was a determined spirit who loved singing and writing songs. She doesn't carry herself as a woman who knows her five-octave-range voice, one of the most identifiable of her generation, has led her to produce several multiplatinum albums since her eponymous 1990 debut and rack up an estimated net worth of £365m. Her most successful album, Music Box, released in 1993 and certified diamond, sold 32m copies worldwide. Her most recent studio album, Me. I Am Mariah... The Elusive Chanteuse, released in 2014, sold a tiny fraction of that, however, and the last time she toured Europe was 2003. This time, she wants to make sure everything is right. After that she will continue her residency in Vegas. "I love everything to do with music, I love the creative process, my favourite place is the studio. I love writing songs. To me that's the best gift."
She's been writing songs since she was six. She used to sing underneath the table because she felt that was the only way she could express herself. "It was cathartic," she says. "Suddenly I'd come up with a melody. It would come from out of the blue."
Prepping for the tour seems less creative. She nods. Does she have a special diet? An exercise regime? "Yes. My diet is very bleak." Bleak is one of her favourite words. She giggles. "I overuse the word because there is a lot of bleakness going on. My bleak diet is horrendous, but I don't want to tell anyone about it because it's none of their business." She looks tiny. Even her much-photographed breasts are reined in. Whatever it is, I tell her, the bleak diet is working well. She sinks further back into her pillows. "I just don't want people commenting." It seems she is hurt by nasty comments. I saw a photo of her online recently eating ice cream. "Ice cream? Not on the bleak diet," she says. "That must have been very old."
She's losing her voice a little and rasping. I read that she sleeps with 10 humidifiers. She nods. "I need them. At least four or five around my bed. I also like to have a steam."
Her children will be going on tour with her. "My son keeps asking, ‘Can we go on an aeroplane?' They've been travelling since they were three months old."
Monroe, named after Carey's longtime girl crush Marilyn, likes to sing. "She was singing last night with her friend. I can tell she has a really good ear she can mimic what I can do. But she's only 4½ and it's not fair for me to push it on her, so I am allowing her to be who she is. At the moment, she would rather just be silly with it. She knows she's named after Marilyn, and she can recognise her in pictures, but I haven't shown her the movies yet. They are into Disney and Halloween."
She had a difficult pregnancy: pre-eclampsia, gestational diabetes and it was suggested that the twins be induced at 33 weeks. She refused, because she didn't want to be separated from them by an incubator when they were born. "I wanted to keep them with me as long as I could, which was until 35 weeks, and that worked out well."
There's a flutter of her luscious eyelashes. I admire her diamond butterfly ring, but then notice the engagement ring. It's not so much a rock, it's a brick.
She met Packer in Aspen, where she goes every year for Christmas. "He and my friend Brett Ratner [a film director and producer] are partners in business," she says, "so he invited me over. I didn't feel like leaving the house, but I went anyway. This was about two years ago, and I didn't see him again until I was at a movie premiere. We started talking, joking around, stuff like that." What's his business with Ratner? "They produce movies. That's not his entire job, but that's one of them."
She once said that growing up without a strong male figure in her life on a day-to-day basis affected a lot of her decision-making. "My perspective on that has changed. I don't think it was because I was without a father figure, I think there were lots of elements about my childhood that made me who I am. Some made me stronger, some made me more vulnerable. It was a combo plate."
So what's on her combo plate now? "Oh my gosh, it's just way too full." Does she feel happy? "Sometimes. You just have to find the comedy in everything. There's so much nonsense that's just not worth spiralling over.
"I had the whole summer off. I was relaxing with the kids. Right now, there's a lot on. I do really enjoy performing. I like having an experience with people, trying to make them feel that they are not just watching an untouchable person. I want them to feel like they are in my living room."
Indeed the dress she's wearing now in her living room, a figure-hugging black maxidress, looks more like a tour outfit than a lounging in the house outfit. "I am wearing it because I went to an event," she says, "but I can lounge in this it's stretchy." Although her high heels have been cast off, she still walks on her toes. "Ever since I was a little girl I liked to walk on tippy toes, like a Barbie. My babysitter used to say I was walking like a Barbie. I only had one, and I cut its hair. Then I went to beauty school, but dropped out. I was singing and working in Manhattan, and I didn't have time for those early morning classes. But I feel that I've learnt in life because I've worked with almost every great hair and make-up person there is. I never wear red lips they just don't look good on me."
She describes her ideal day as "lying on the beach without a camera or a phone, surrounded by pink sand and the water". That sounds a little honeymoony. Is the wedding planned? "It's a secret." It's really happening, though? She waves the brick at me. "I'm not doing this for laughs." That ring is pretty hilarious. "I enjoy it. When you grow up without a lot of things... I try not to take things for granted." Still, she has two failed marriages. Is she not burnt from the experience? She looks very serious. "I am very traditional. I have babies, it's more appropriate. I don't know if most people can relate to that, but that's just how I feel." She won't elaborate on the relationship itself, however. "If I start talking about this relationship, people will interpret it in their own way, so I think it's safer for everyone involved to just not talk about the very personal aspect."
She describes herself as "content, but also very busy". Her voice is now cracking with exhaustion. "I am a private person." A very private person who, thanks to all these cameras, now has no privacy. "It's a big thing for me. Yes, it's annoying. I wanted to document this tour because I don't know when I am going on tour again. I wish I could have documented other tours. I am doing it for the fans they'll love it."
She doesn't enjoy being snapped by the paparazzi, however. So many contradictions. "I am a pretty insecure person," she says, "but I have to get over that because this is the reality of my life. I look better than I looked a few months ago, but I am definitely not one of those people who says, ‘I look amazing today.' I have to point out this is a rented house I would never have overhead lighting. High hats, they call them. In my apartment in New York, it's all recessed lighting, chandeliers, candles. This lighting is abusive."
Dita Von Teese recently told me in an interview that she insists on pink walls and no overhead lighting so you look good naked. "You still want to look good with clothes on," says Carey. "When I was pregnant, I had a house with lots of antique mirrors on the walls, so as I walked around I couldn't help but look at myself this huge pregnant woman. I hated myself for decorating the house with all these mirrors. I was so mad at myself," she laughs.
When I leave, at 1.15am, her manager tells me that my whole life is going to change now Mariah has shed her light on me. Her fairy dust has been showered.