'Come anywhere nearer and I'll bite you in the ass." Joan Rivers is doing battle with the Independent on Sunday's photographer in her suite at The Ritz. "But Joan, you look fabulous," he says, trying to reassure her. "Yeah, right," she replies acidly. "Who are you trying to kid? At my age it's all you can do to look alive. Now keep your distance, or you'll crack the lens."
As anyone who has seen the New York comedian in action will know, this is a classic Rivers exchange: sour, sarcastic and self-mocking. Still, you can see her point. Though physically she's a lot smaller than you expect - even in stiletto heels she barely reaches my chest - from a certain distance she is really very glamorous. Look closer, however, and it all gets a little otherworldy. While her eyes seem to have been yanked simultaneously upwards and outwards, giving her face an expression of frozen astonishment, her nose has been chiselled, chipped and sculpted into a perfect Upper East Side ski-jump. Add to that the false eyelashes and the fashionable fly-away hairdo, and the overall impression is of Barbie caught in a wind-tunnel.
Of course, Rivers is the first to poke fun at her efforts to stay young. At 71, she says, her best friend is Botox while her three-year-old grandson Cooper calls her "Nana Newface". It's with wonderful aptness that she is soon to play a patient in Nip/Tuck, the TV-drama series set in a plastic surgeon's clinic. Rivers learned early on in her career that if you dish it out you have to be able to take it.
Self-deprecation is crucial to her schtick, as well as an extremely effective defence mechanism. There's nothing that anyone else can say about her that she hasn't already said herself, doubtless with considerably more cruelty.
Perhaps most impressive is Rivers' ability, after 40 years in the business, to stay ahead of the game. During the Eighties she would talk about faking orgasms and visits to the gynaecologist; now, of course, it's all body fluids and sagging genitalia. Where Elizabeth Taylor and Martina Navratilova were once her prime targets, these days the biggest tongue-lashing is reserved for the Hilton sisters ("You know you're gonna catch something with them") and Monica Lewinsky ("Oh God. One of the all-time stupidest bitches"). Rivers swells with pride when she tells me how last month, on the Jack Dee-hosted show Live at the Apollo, her jokes about terrorists and 9/11 widows were cut out by the BBC on grounds of bad taste. "I understood why they did it but this is what we're living in now," she protests. "If you can't talk about that, what the hell can you talk about?"
It's by no means the first time that Rivers' mouth has got her into trouble. Since her stage debut in the late Fifties, holding forth about the importance of marrying for money and looking your best to keep your husband, she has stood accused of setting the cause of feminism back at least 50 years.
"What nonsense," she barks. "I've worked harder for women's rights than most. I've broken every barrier there is to break. As I always say in my show, 'tell me it's not true'. Don't tell me you don't want to have somebody to love you because that's bullshit, don't tell me you don't want to look good because that's bullshit too. We all still want the basics.
"I once had a big fight with [the writer and activist] Gloria Steinem who sat there and told me how wrong I was. Don't misunderstand me, I think she's wonderful, we've marched together. But you have to face life too. I said to her 'You're sitting here, you've just come from a waxing, you're hair is bleached, you look beautiful. You've probably had a nose job. And what is so terrible about that?'"
Even now, Rivers insists that she's a keen advocate of family values: "If you can find some rich old pig to sponsor you, let me tell you, this is heaven. And then you can do what you want to do." But Joan, I say, you're not short of a bob or two. "So what?" she cries. "I'm still looking for my own Onassis. I know that out there there's some rich guy willing to support me."
And you'd give it all up for a man?
"Well, perhaps not," she reflects. "But my rich old pig would say 'Joanie, Joanie, you do what you want. Sponsor a movie? Of course, darling. You want to star in it? Well why didn't you say so?'"
As well as being the most straight-talking woman in show business, Rivers is also among the most hard-working. Along with the stand-up - next week she takes her Broke and Alone show on an 11-date tour of the UK - she's in the midst of recording The Joan Rivers Position, a chat show on Five in which she appears as an agony aunt. In America, a large part of her time is spent flogging costume jewellery on the American shopping channel QVC. Since the jewellery took off she has also branched out into cosmetics and skincare products. More recently she and her daughter Melissa have carved a niche conducting red-carpet interviews before Hollywood awards ceremonies during which they cast an acerbic eye over celebrities' sartorial habits. You mean they actually come over and talk to you?
"Why wouldn't they?" replies Rivers, shooting me a butter-wouldn't-melt look. "Usually the bigger they are, the more they can relax and laugh about it. Julia Roberts isn't going to get upset if I don't like her dress. Those four Sex and the City girls - they think it's hilarious. Remember, we're only talking fashion; let's calm down here. But there are the middle-ranking ones who are very insecure about themselves and who take it seriously. Kevin Costner got furious because when he brought his fiancée over, I said 'Let's have a look at the ring.' I mean, you couldn't find it. It made all the papers the next day. He was furious. I mean, come on, the man makes millions. He should just laugh it off and buy the girl a bigger ring."
Rivers' unstoppable riffing, by her own admission, masks a deep seam of insecurity. Even now she's terrified that the work might dry up, that the rug could be pulled out from under her feet at any time. "It's happened before, twice, so there's no reason why it shouldn't happen again. It's a very transient business. Listen, how many people have you interviewed who have disappeared without trace?" A few, I say. "See? You can't pause for breath in this industry and it's all over. You can't afford to take your eye off the ball for a second."
In 1988 the television station Fox pulled the plug on Rivers' late-night chat show after a dip in the ratings. Not long after, her British-born husband and manager Edgar Rosenberg, who had been suffering from depression after undergoing bypass surgery, checked himself into a Philadelphia hotel and committed suicide. The finger of blame was immediately pointed at his wife, from whom he'd recently separated. "It was awful, just terrible," recalls Rivers. "I was crucified by the press and my daughter stopped talking to me. Thank God we're very close now. After that there was no work, I couldn't get arrested. So I had to leave California, go to New York and start over."
After months of therapy, Rivers eventually got back on her feet and launched her jewellery line; by the mid-Nineties Joan Rivers Worldwide Inc was turning over US$25m a year. But her career was to fall apart a second time when her business partner absconded with all their profits. "You wake up at 65 years old and realise you owe US$38m," Rivers says. "At that age, you can't turn tricks. To get my name back, I had to pay off the shareholders. It was terrible. But I've got a great lawyer who got me through it. Twice a year he comes to my house and stands on a pedestal and we all bow down."
Though she still goes on the occasional date, Rivers believes she'll never marry again. Two years ago she ended a nine-year relationship with Orin Lehman, a New York banker and former Commissioner for Parks. "I had to give up a lot. As you get older, you get cynical and it gets harder to fit other people into your life. I'm working very hard now because there's no one I want to stay home with. When I get a chance to go on tour, I jump at it. I get to go to all these places that I've never been to before like Wales and Devon. We're going to Torquay on this tour. I've never been there, I hear it's full of old people. For all I know I could meet my Onassis there and stay there until I'm dead."
Rivers was born Joan Molinsky in Brooklyn, New York, to Russian immigrant parents. She says her biggest inspiration has been her mother. "She was very strong, never complained about anything. It was years after she was dead that I realised it wasn't that great a marriage, and that she was very lonely. She just held her head up and got on with it. She looked like a great dowager, always dressed in pearls. I thank God that she lived to see me successful. As a parent now, you just want to know you're child's going to be OK." When she was a teenager her parents warned her off comedy - they felt it was an unseemly occupation for a woman - and it was at their insistence that she went to university. Rivers attended New York's Barnard College and, in 1954, graduated with a degree in psychology and anthropology.
In her early years as a stand-up she played small New York dives where a hat would be passed around at the end in lieu of payment. For a while she worked as an actress, appearing in low-key productions alongside Barbra Streisand, Bill Cosby and Woody Allen. Her big break came in 1965 when she appeared on The Johnny Carson Show, though it wasn't until 1983 that the show broke with tradition and named Rivers as its permanent guest hostess, a position she held for the next three years.
Even now Rivers says she gets stage fright. When she walks on stage she gets her warm-up act to award marks out of ten on the audience mood. Anything above seven is great, five is workable. Anything less than that and she knows there's hell in store. Her nerves are even worse when she's acting. "I hate anyone coming to see me in the dressing room before a show. I've been on Broadway now four times and I still think I'm going to forget my lines."
It's with a typical mixture of haughtiness and anxiety that Rivers tells me that retirement isn't an option. "They'll have to drag me off the stage in a box. I have a lifestyle to maintain, and that costs money. If I stopped work, I'd drive myself crazy thinking about all the opportunities I'd missed. I have this running joke with my daughter, I tell her 'I haven't peaked yet'. I always think there's something better around the corner.
"Anyway I can't have all those other comics getting too big for their boots. If I have one more of them come up to me and say 'I owe my whole career to you', I still think 'Listen you little bitch, I'm still going to wipe you off the stage'." She pauses, leans forward in her chair, and whispers conspiratorially: "And I always do."
'Joan Rivers - Broke and Alone in the UK': Gaiety Theatre, Dublin, tonight, and touring to 18 Oct (tickets: 0870 242 2898). 'The Joan Rivers Position' begins tonight on Five