For Hollywood it had been a major event — one of its greatest stars had reached his 70th birthday last year and the great and the good of tinsel town had gathered to make sure the event was special.
In fact the guest of honour was one of the first to leave. "I'm sure you understand," Robert De Niro said. "But I promised to have a drink with Diahnne." To which his wife of nearly 20 years, Grace Hightower, smiled and said: "Give her my love."
Diahnne Abbott and Robert De Niro had divorced in 1979 after only three years of marriage but with Grace's knowledge and approval, Diahnne remained his best friend. Before he ever made an important decision, he always asked Diahnne what she thought.
Now a small dark-haired woman of 69, Diahnne toasted the 70th birthday of the man to whom she was probably closer than anyone else on earth.
"You were a lousy husband," she told him. "But you're a wonderful father to our children. And you'll always be my best friend whether you like it or not!"
The couple first got together in 1970 and, despite De Niro's subsequent succession of sensational affairs, they remained inseparable after the divorce.
"We maintained separate homes and separate lifestyles," Diahnne said. "But both knew that when one was in trouble or needed help the other would drop everything and be there. And that's how it's been ever since."
When they met, De Niro was a struggling Hollywood actor and she was an actress-singer who was filling in between jobs as a waitress, but it wasn't until 1976 that they finally got married.
Diahnne came with a ready-made family — a young daughter, Drina, from a previous marriage and whom De Niro formally adopted. Now De Niro's lifestyle changed dramatically. No longer did he live in rented rooms, share taxis and hoard his small change for fear that one day his luck — and his money — would run out. He bought a mansion in Hollywood's palatial Bel Air district.
Once almost obsessively antisocial he now gave dinner-parties with his new wife. "He absolutely doted on Diahnne," said director Brian De Palma, a close friend.
"He wanted everyone to know how lucky he was to have married such a marvellous woman. He started to go to parties — something he had never done before — so that he could show her off."
In January 1977 De Niro's happiness was complete — he became father of a son, Raphael, named, he claimed, after the hotel in which the child was conceived. A close friend, Shelley Winters, quipped: "Thank God they weren't staying at the Algonquin!"
But family life, idyllic though it was, simply wasn't enough for the restless De Niro and soon his eye and his mind started to wander.
When Diahnne found he was having a serious affair with singer Helena Lisandrello, she threw him and his belongings out of the Bel Air mansion.
"I miss Di and the kids terribly," De Niro told friends. "They are always on my mind. I hope we can all get together again soon." In the meantime he was seen constantly with Helena Lisandrello, a stormy relationship which would last for 14 years.
Then she told De Niro she was pregnant. He was furious and insisted on an abortion but she refused and in September 1992 a daughter, Nina, was born.
Eventually De Niro relented, fell in love with the baby and gave Helena $50,000 "to buy things for my kid". He also bought Helena a sports car and a complete new wardrobe.
Now De Niro's private life became even more complicated. He was still technically married to Diahnne, whom he saw regularly, lived much of the time with Helena, was dating model Doris "Toukie" Smith... and also apparently seeing pop superstar Witney Houston.
His name was also being linked with 19-year-old UK supermodel Naomi Campbell and with his co-star in the movie Mad Dog and Glory, Uma Thurman.
Shortly after his 50th birthday, when his relationship with Toukie Smith had apparently been over for two years, the couple became the parents of twin boys... the children were born through a test-tube surrogate mother.
The news caused a sensation and even more so when De Niro announced that he and Toukie were not getting back together, but would share the parenting of the children.
Then his private life was once more in the headlines when he married actress Grace Hightower in 1997. Diahnne Abbott was delighted. "She is perfect for him," she said and the two became close friends — and still are.
"Nothing Bobby does astonishes me," Diahnne says. "He lives by his own rules. So long as you realise that I guess you can learn to put up with anything!