You wouldn't find Julia Roberts sucking a furtive fag in an alleyway round the back of the London Palladium, but that's where Whoopi Goldberg is. Standing by the wheeliebins, dragging on a Marlboro, flirting with stagehands and musing on why her film Sister Act was so successful. "I was funny," she says in that familiar two-packs-a-day voice, "and the music was great."
Quite right. Nuns singing Motown proved hugely popular, and Goldberg was fizzy and fun as a club singer on the run, hiding out in a convent. It was the third of three fine performances - including a debut in The Color Purple and an Oscar-winning turn as a psychic in Ghost - that made her the highest-paid female actor in Hollywood in the early 1990s.
Defying the rule that says stars need to stay anodyne, she used her fame as a platform for her outspoken views on issues from abortion to taxation. Bill Clinton benefited greatly, and provided her with a police escort to his inauguration. John Kerry ran a mile from a rude joke she made about George Bush (it wasn't subtle - just think about the name) but the Obamas know the value of her backing: during the election, Michelle used the informality of Goldberg's TV chatshow to fight off rightwing claims that she was a black separatist.
Goldberg has a political clout in the US that we don't see over here. She's instantly recognisable, obviously cares deeply about stuff - not many stars who back charities fighting homelessness and drug abuse have experienced both in real life - and is unfailingly frank, even about her friends: "It's great to see Barack as president, but there's a lot to get done and he really is in the stuff. There's no money and everybody's out of their minds and pissed at America."
So let's be equally frank about the stage version of Sister Act, which is the reason she's in London. It opens at the Palladium next month, but don't buy tickets expecting to see Ms Goldberg - "Hey man, just Whoopi" - recreate the role of Deloris, 17 years on. "I'm not in it," she growls, staring over purple oval granny glasses that never get pushed up from the bridge of her nose. "I am 112, so I was too old." She's 53, actually, but there are little twists of silver in her dreadlocks these days and Deloris is a young woman. "I also don't sing."
Watch the film again for overdubs and you'll see that's true. But here's an even bigger bombshell about the live version: "The music is not the Motown music that you know." What? No My Guy sung as My God? "We were not allowed to have it." Instead a new score sets gospel songs down on the disco dancefloor. "You recognise all the disco licks, so you're OK with it," she says, loyally. "And the girl we've got instead is great."
Her input seems to amount to watching rehearsals in London for a few days - but even that is a bit of a miracle, because fear of flying kept her off planes for 13 years, until now. "I saw something that built in my mind," Goldberg says, "until it became such a big thing for me that it was just impossible to fly." What she saw was a mid-air collision. Her way of coping was to travel in a personalised tour bus, or on the QE2. So why confront those fears now? "They dangled a cheque in front of me," she says, cackling. "But I got really nervous and started sweating a few days before."
How was the flight then? "Hmm. Was it still tough, uncomfortable? Yes. But not 'undoable', and that was the difference. I didn't look around a lot." Were the crew helpful? "Well," she admits, reluctantly, "the man that I'm working for sent his plane." Private jet? "Uh-huh. The thinking was, 'If I do freak out, nobody knows. No one writes about it.'"
If she had, she would be more likely to draw sympathy than ridicule. She doesn't dress like a star, in her jeans, a black T-shirt and a baggy white smock, but when a couple of young women run up from the street, begging for a photograph, she gives them a full-beam, professional smile. Strangers warm to the look of her, but then even the name turns up the corners of your mouth.
Caryn Elaine Johnson got her nickname from a whoopee cushion, because she farted so much. Not that her childhood was bursting with laughs. Born in New York in 1955, Goldberg was dyslexic, she dropped out of school, left home, slept rough for a while and became addicted to heroin. A drugs counsellor helped her get clean, but by the age of 20 she had married him, given birth to his child and got a divorce. She worked as a bricklayer and a makeup artist in a morgue, while trying to make it as an actor and stand-up comedian (having taken Goldberg as a stage name in honour of Jewish forebears). Then Steven Spielberg saw her one-woman routine about ET and cast her in The Color Purple. "I turned it down at first," she has said, "because nobody wants to suck." But she was mesmerising as Celie, the lead in a film that changed the way black actors were perceived.
Oprah Winfrey was the other woman who transformed a part in that film into a prominent role in American society. But while Winfrey is orthodox, Goldberg is still wild. Three times she has been married, and three times divorced. Having been a teenage mother, and the daughter of one too, she couldn't exactly stamp her feet when her child became pregnant. Even if Alexandrea was only 14. "That was kind of startling," she once said, but she was supportive. "I said, 'OK, we'll all band together and help you do this.'"
That meant enlisting her own mother, Emma, to hold the baby while Goldberg and Alex made movies. They were in Sister Act 2 together, although the mother-daughter act didn't last long. "Oh, she's a terrible actress," Goldberg says, laughing. "Terrible." Has she said this to her daughter? "Yeah," she says, drawing the word out to suggest it was tricky. "I've said, 'It might not be for you.'" Alex, now in her 30s and a chef, lives in California with her three children.
Goldberg has not retired from acting herself, despite saying she would. "I have slowed it down to almost a crawl, but not stopped. What would I have done?" She has revived her one-woman show to great acclaim, and is the moderator on ABC's The View, which is like Loose Women only with stratospherically more important guests. Condoleezza Rice, for example, talked with remarkable candour about being single. "People say you've dedicated so much to your career that you're really shorting your personal life, but the truth is that I've never found anyone I wanted to marry," she said on the show.
Goldberg sympathised, so is she single now too? "I don't know," she says, smiling and looking over her glasses again. "I don't think I'm single, but I'm not totally committed. I'm not very good at relationships. I wish I was, but I'm not. I gave my child all the time and money that I had, now I want it for me.
"It's hard to make the space [for a relationship] when there are so many other people in the room." Not literally: she lives in a Manhattan loft in SoHo with a cat named Oliver. "I am selfish. I like being able to get up when I want, go where I want. It's hard. Unless you meet somebody that really knocks your socks off, I think it's not prudent to spend a lot of time you don't ... mean." Her socks are still on then? "Well. They're stockings now."
The homebird even stayed in on inauguration day, after panicking about the crowds. Having "screamed out of my window" when Obama won, she saw his swearing in as "the end of something, as much as a beginning. As little kids, we were taught that anybody could become president ... but anybody never was. That's a hurdle we have now dealt with."
There are now higher hurdles. "It is an almost impossible job, not least because of the damage done by George Bush. Never before has America been so alienated. For a little while there we were like, 'Fuck the rest of the world, we don't need you.' But we do. They tried to dismantle the UN and get rid of Nato. I mean, who did we think we were?"
Not that her anger is confined to the former US administration. "I saw the leaders of Germany and France saying the crisis was a defeat of America. You gotta go, 'Whoa dude, what are you talking about? Your bankers saw the problem and went, 'Hey, stop that you'? No. They all deregulated and got as much money as they could, then said, 'It's not working, see you, bye.' As usual, the people on the lower half of the ladder get fucked. It's always been that way, but it has never been so ... despicable."
No wonder windows get smashed, but mention of that makes her fret. "Yell and scream all you want, but to destroy stuff? It's not one bank, or the people; it's a system of banking that's the problem. Also, if you start to break the windows, that means its OK for the other guys to come and break down your door."
She has thought about running for office, but says there are "still skeletons in the closet" and fears attacks of the kind the Obamas faced. "Everybody was freaking out about his pastor, Jeremiah Wright, saying, 'God damn America.' They were saying he's a racist. I said, 'Yeah, he's a fucking racist. He went and fought in world war two, came back and had to ride in the back of the bus. He's pissed. If you know your history you know there is a certain generation of black folks who are not happy. If you pretend that that is a shock then you're full of shit too.'"
Last year Danny Glover, a co-star in The Color Purple, told me he was worried Obama would turn out to be just like any other career politician. "I don't think he's right," says Goldberg. "Will Barack Obama turn out to be what everybody wants him to be, this messiah walking on water? That, I don't think will happen. Is he going to try to get some shit done? Yeah. Is he gonna work his ass off? Yeah. I just want to see somebody try. After the last eight years, that's all the fuck I really want."
In her own words
On The Color Purple "I told her [author Alice Walker] her I would play a Venetian blind, dirt on the floor, anything."
On looks "I don't look like Halle Berry. But chances are, she's going to end up looking like me."
On acting "An actress can only play a woman. I'm an actor, I can play anything."
On the war on terror "If you're anti-war and you tried to explain your stance, it didn't matter - particularly in the entertainment industry. You were labelled unpatriotic, which is kind of dopey, because if you're anti-war it means you don't want anybody to die."
On politics "I don't really view communism as a bad thing."
On the election of George Bush " The country got a new president who has kindly given me a lot of material, and I got the menopause - so I guess we're all going through shocking changes."
On driving "I don't like driving very much. That makes me very unhappy, because I scream a lot in the car, but other than that, life is actually pretty good."
On life "Normal is nothing more than a cycle on a washing machine."