There are three great rules to celebrity interviewing. First, go through the cuttings files to see what has already been written; second, read their biography (or several); third, check the day's news for any change in status or circumstance.

This extensive prep does the trick for most celebs - but not for Joan Rivers. Remarkably for an 81-year-old, the comedienne remained one of the world's funniest, dirtiest and most transgressive stand-ups. Keeping a handle on her activities - and opinions - was always a 24/7 job as she was rarely out of the headlines.

Take the week before our chat. Joan was busy promoting her latest book - Diary of a Mad Diva - across the States. An invitation to appear on CNN quickly turned sour when the feisty Rivers accused the interviewer, Fredricka Whitfield, of adopting a negative line of questioning. Within minutes, the footage of her storming off the show had gone viral and every US network wanted her verdict on the so-called effrontery.

Rivers's publishers were no doubt counting their chickens with so much free press, but the birds had barely come home to roost before the cosmetically-enhanced whirlwind was tearing a strip off Hamas on camera at LAX airport.

Rivers had been on her weekly bi-coastal commute to film Fashion Police for the E! network when she was cornered by a reporter. Voicing her support for Israel in no uncertain terms, she attributed the casualty figures to "Palestinian stupidity". Criticism across the social networks was instant, though the Huffington Post alluded to her originality for being the first to use a hypothetical analogy.

Sure I do a lot of Anne Frank jokes. But it makes people remember what happened to her

"If New Jersey was throwing missiles at Manhattan we would bomb the hell out of them," suggested Rivers, which is precisely what she had said to me a few days earlier when the Israel question arose and she buried her head in her hands.

"I was so upset I couldn't discuss it without going crazy. I had a dinner party one evening and nearly had a fight with one of my guests while discussing the situation. The world is so antisemitic now, it's terrifying. It's frightening, horrible. The joke is that if Israel did what the world wanted, would they really like the Jews any more than they do?"

Rivers's last visit to Israel was four years ago and her intoxication with the spirit of the country and its ability to survive against the odds shone brightly. Interestingly, the woman born Joan Alexandra Molinsky in 1933 to Russian-Jewish immigrants shared similar traits and her energy, stamina and aggression enabled her to remain significant as a performer for more than 50 years while jumping huge hurdles. Her struggle for stardom, bankruptcy and heartbreak in widowhood following the suicide of her British-born husband, Edgar Rosenberg, in 1987 were dealt with in her first two autobiographies - Enter Talking and Still Talking. But having reached book number 12, she was enjoying the luxury of simply musing.

"At least that's what my editor told me to do. 'If something amuses you, write it down,' she told me. So I did. The book is written as a diary, but not to be taken seriously as there were some days when I didn't write anything at all. I know the doorman at my building, who has been there for 22 years, was very upset because his birthday was just a good day and I had nothing to write."

Fortunately, there were many other days when the words just flowed. True to form they are as scathing, vitriolic and hilarious as one would hope and squarely aimed at the chins of celebrities, notably those of Gwyneth Paltrow, Girls' Lena Dunham and the Kardashians. The book is, in fact, dedicated to Kim Kardashian's husband, Kanye West, who is quoted on the first page as saying: "Sometimes people write novels and they are just so wordy and self-absorbed ... I am a proud non-reader of books."

"It was an obvious dedication as I knew he would never read it," Rivers laughed. "That's some role model when you think he has a kid. Education and keeping the mind open is everything, but no one agrees with me any more in the United States.

"It used to be that when immigrants came to America they made sure their children were better educated than they were. That doesn't happen any more. Now they expect everything to be done for them."

Reading to her daughter, Melissa, now 46, and her grandson, Cooper, 14, was one of Rivers's great pleasures - and a warm memory.

"When they were younger and went to a book store they could have anything they wanted. They didn't have to ask. The only rule was they had to start the book, but only finish it if they liked it. Reading should be a pleasure not a chore."

Reading Rivers's books has never been a chore for her fans, who whizz through her pseudo-diary containing entries that are as compellingly cruel as "January 14. Dear Diary: Red-eye in from LA. Found myself sitting next to someone who was the spitting image of my cousin Leon. And I say spitting image because he was spitting. Every time this guy spit he washed down the seats of not only the people in front of me, but the people in First Class. I haven't been that wet since I went through the menopause. I couldn't sleep and sleep is important... Which is why I always request to sit next to Stephen Hawking. He doesn't toss and turn and his keeper, God bless her, wipes off not only his spit, but dries off the entire cabin." Assaulting the reader with her merciless humour is what Rivers believed she was put on earth to do."Make people laugh and you give them a vacation," was her first line of defence.

Of course, there are entries in her book and in her stage show, poignantly titled Quick... Before They Close the Lid (which she had intended to bring to the UK next month) that would not sit well with everybody. And though the option is not to buy, it doesn't stop the complaints.

Among the many red flags raised is Anne Frank, that other diary writer who crops up when Rivers's friend Bambi compares them in the book.

"Who the f*** does Bambi think she is?" writes Rivers. "I'm nothing like Anne Frank. She lived in a walk-up; I live in a penthouse. And unlike Anne Frank, I do things. I go out, I shop, I go to the theatre." It's fighting prose, but Rivers the warrior was always ready to defend it.

"Sure I do a lot of jokes about Anne Frank. But when you do those jokes it makes people remember what happened to her. That process of bringing her story back doesn't have to be a serious one. What I say is all nonsense, but it helps to keep her memory alive."

On that note, Rivers last year decided to get a half-inch tattoo on the inside of her left arm. And when she raised it, the 6M was clearly visible. "I went with my friend Margie, so there were two old blonde Jewish women entering a tattoo parlour in the village. The girl on my right was getting her entire back covered with a butterfly and the guy on my left wanted his life story on his leg." That's all she would say about the tattoo. But with the story of her own people etched on her skin, Rivers proved herself again.

Her bolshie confidence was facade. Asked if she still got butterflies before stepping on stage she replied: "I get butterflies before I go out to say hello at a party." It's a response that will surprise those who think she was a sadistic comic who fed on the dangerous material she created, when the reality was quite different. It was borne out by her decision to stop writing her real-life diaries for fear of hurting others.

"I realised if you put down the truth, it would hurt someone who read it after you were dead. If you have a fight with your husband and write, 'Fool, why did I marry him?' the next day everything would be wonderful again and then they'd see it in years to come and think, 'Oh, my God'."

Protecting the people who matter was her priority and she hosted all the festival dinners and was anticipating a full table for Rosh Hashanah.

"My mother loved entertaining and I've followed suit, so we have big celebrations for New Year, Passover, Thanksgiving and birthdays. There's so little time these days as everyone is so busy holding down two jobs, so no one gets to entertain. That's why we love a show like Downton Abbey with its big fancy dinners. I get out all the good silver and make it a really wonderful fantasy holiday."

As for Yom Kippur, Rivers's fast tended to end around lunchtime. "I think God has got bigger things to worry about than me eating an egg at 2.30pm because I'm starving."

Had she lived to fulfil her UK commitments, she would have travelled by tour bus. "It's like being in a rock 'n' roll band, and so much fun because you get to see the countryside from Bristol to Bournemouth."

In a sad irony, she talked about being in good health."I'll just say that nothing is not working."And on the question of her mortality: "If I open my eyes and I don't see candles and flowers then I know it's a good day and I get up. Someone else said that, but it's such a funny line I wish it was mine." Joan, it is now.