"I just went NUTS!" she tells me. "I stopped the whole show, and just SCREAMED at him: 'How dare you! I am not a racist!' I demanded an apology. I stopped the whole show until he finally said he was sorry.
"I bet nobody has come back to him like that before, but you reach a point in life when you just have to say, 'Stop it.' This man had to be stopped, and I stopped him, this disgusting man who has written a stupid movie about what a great father he was even though he didn't see his son for the first eight years of his life. Gah!"
She is furious as she recounts this but, as ever, it is not long before the fury becomes distilled and she turns it funny.
"I'm racist?" she mock-shrieks. "How can that even be possible? I'm playing Blackpool, aren't I? Not Whitepool." Her grin gradually becomes malevolent. "And anyway, I was a friend of Michael Jackson's back when he was black..."
Rewind 24 hours and Joan Rivers is in her palatial hotel suite rearranging furniture. The tiny woman is attempting to heave a chair twice her size. "Here, help me move this thing over there," she says in lieu of an introduction. "I hate to leave a mess." She titters. "I'd make a fabulous gay man, wouldn't I? Always tidying up."
The room's current disorder, I learn, is due to the fact that, for the past hour, she has been having her photograph taken, the photographer deeming it necessary to shift the furniture as she posed. And so we spend the next five minutes moving chairs and repositioning desk lamps. Rivers is a great deal more nimble than her 72 years might suggest.
Eventually, I manage to get in an introduction. "Well OK," she responds, pursing her surgically enhanced pout at me, "hello officially, " and then she perches herself delicately on the sofa, one leather-clad leg crossed artfully over the other. Up close, the infamously sculpted face looks feline, waxy and not entirely real, like a candle without the wick.
"Nice room," I tell her, but before I can press her further on her very prevalent penchant for opulence and luxury, she leans forward to interject, index finger extended like a school ma'am about to scold.
"Listen, I'd be grateful if you didn't mention the name of the hotel," she says of the place she always stays in whenever she is in London. " Why? Because, you know, because of the stalkers, and such."
"Yes, and those people who call and leave messages...."
The pout purses some more, she sips distractedly from her cup of coffee, and then changes the subject so forcefully that I am helpless but to follow.
"So anyway, here I am back in England for another stand-up tour." This is a woman never backwards when it comes to doing her own PR. She scans a sheet on which is printed all 16 dates of her impending nationwide trek, and says: "What can you expect from me? Well, I'll be full of energy in Croydon [the first night], and dead by Blackpool [the last]." She cackles, revealing perfect, and almost definitely false, teeth. "No, but seriously, it'll be great. I always am.
"I've got so much ammunition: Madonna is coming back with a new album, Jordan has just got married and, of course, Michael Jackson still exists. [And, no doubt, the Darcus Howe episode will feature prominently.]
"And when I've done with that lot, I'll get on to the subject of being a grandmother, which I love, and sex among older people, which I don't. I mean, please! You know what safe sex is like at my age? Doing it on the floor. That way, we won't fall out of bed and break a hip." She laughs and, politely, so do I. But not, it seems, with satisfactory force.
"Don't worry, if that joke doesn't work on the first night, I'll have it replaced by the second. See, my shows have to be fantastic. They must! People get dressed up to come and see me. They get into their cars and suffer traffic to have me make them laugh. And so I must send them home afterwards completely satisfied. It's basically my motto." And one that has served her in rather good stead.
After almost four decades in the business, Joan Rivers is still, bizarrely, going strong. In contrast to the usual rules of showbiz, which inevitably favours youth over experience, she has doggedly refused to become, like so many before her, outdated and outmoded. Instead, refusing to mellow with age, she remains delightfully foul-mouthed, a crinkly with attitude.
"I'll tell you what I'm doing right," she barks in that foghorn New York drawl. "Basically, I live in the present. I can't stand all that bullshit about the good old days. As far as I'm concerned, I haven't even peaked yet. I'm convinced that there is something big just around the corner waiting for me. Maybe it's a play, a movie, or another big TV show. I've got a recurring role in Nip/Tuck, you know I play myself and I guess that has made everybody sit up and take notice. So trust me, my best is yet to come."
I ask her if she ever considers retirement, and the frown she comes back with battles against its botox paralysis to become thunderous. "Gah! Please, what a dreadful idea! And why should I? Let's face it, I'm funnier than ever. Especially around young people. I'm anti-age, you see, I hate old people in general. I'm even disgusted by my own age, so I try not to think about it. I know that the end is near now, that I could go any second, but while I'm alive, I want to surround myself with youngsters. Old people tend to be such miserable bastards, don't you find?"
The daughter of Russian immigrants, Joan Rivers (originally Joan Molinsky) was born in 1933, and grew up in Brooklyn. Her early attempts to become a serious actress were unsuccessful, but casting agents kept telling her that she was funny, very funny, and so she turned instead to comedy.
After a decade on New York's comedy circuit, she landed her big break in 1965 with an appearance on The Tonight Show with Johnny Carson. Within three years, she was fronting her own TV talk show, and followed this with a self-penned Broadway hit, Fun City. By the mid-Eighties, she was probably the most celebrated, and certainly the cruellest, funny woman on the planet.
In 1987, at the height of her commercial success, tragedy struck when her husband of 20 years, Edgar Rosenberg, committed suicide following a nervous breakdown. While his wife was in New York having liposuction, Rosenberg locked himself into a Philadelphia hotel room and downed a lethal mixture of vodka and Valium.
Rivers was devastated, but promptly threw herself back into work, stitching the tragedy into the fabric of her routine. One of the first jokes to come out of the episode was one in which she blamed herself for his death: " We were making love and I took the paper bag off my head."
"It was essential," she stresses, "absolutely essential for me to throw myself back into work as soon as possible. How else was I going to pick up the pieces of my life? And how better than with humour?"
The method, she says, worked for her and she remains so convinced that it can work effectively for others that she now regularly lectures on how to survive suicide and deal with depression, a subject in which she has much experience.
Eight years on from her husband's death, Rivers suffered the kind of professional blow that would finish off many a lesser mortal. She had spent much of the 1990s raking in an absolute fortune by designing, and personally selling, garish costume jewellery on the shopping channel QVC. Annual turnovers were rumoured to be in the region of $25m (£14m).
But in 1995, a former business partner floated Joan Rivers Worldwide Inc on the stock market without her prior knowledge, before absconding with $37m. He was eventually caught and jailed, but the money was never recovered. Rivers has been paying the debt back ever since. While there is a direct correlation between her perennially heavy workload and this most awful debt, she insists that her main motivation remains a deep love for what she does. Life, she says, has been good to her, and she has very few regrets.
"Apart from one: I wish I'd married a billionaire. I was dating a Greek tycoon for a while, but, sadly, it didn't work out. What can I tell you? He had the money, but the baggage as well, and so he had to go. That's my only regret. Being a billionaire's wife," she considers, "would have been fun."
Joan Rivers's 'First Annual Farewell Tour' begins in Croydon this Friday, and runs through to 5 November in Blackpool. For tickets, call: 08712 200 260Reuse content