"He hated Rainier and Grace. He claimed he had made modern-day Monaco what it was. He had attracted big money to the principality and started its banking.

"The Rainiers happily allowed him to develop Monaco, but when he wanted some control over developments, the couple refused. They found him far too vulgar.

"He was very bitter with the Rainiers and was determined to fix them up. But he died before he could fulfil his vow."

Frank describes Onassis' lifestyle as decadent. His parties were legendary throughout Europe. Frank says: "He loved showing off to people, having power over them. He'd offer women money to drop their clothes in front of visiting foreign businessmen.

"He hated the pretense of many women who acted demure, and he loved proving all of them would do anything if the price was right."

Frank says Onassis was a "party animal" because this was where the former Greek peasant could flex his power before high society.

"At every party he had to have the most voluptuous women, many of whom were married. One of my jobs was to approach the women in hotels, restaurants and shops. It was all to do with this thing he had about women being low and how money could buy them, even happily married ones.

Frank says Onassis would treat his hired female guests with contempt, slapping them on the buttocks or tearing off their clothes in front of guests and verbally insulting them.

"He was the most vulgar man I'd ever met. But despite all the women around him, I never knew of him going to bed with one."

The only women he seemed to have a modicum of respect for was Maria Callas. Says Frank: "She never stayed overnight. He got along with Maria Callas because she was Greek and talented.

But Onassis had many affairs with young men. His favourite was a tall, blond, effeminate Roman lad called Juilio - "Ari's 22-year-old stud."

Says Frank: "Juilio was always hanging around Onassis. When Ari was feeling amorous, he'd demand Julio's presence in his bedroom."

Frnak says Onassis believed there was nothing wrong with homosexuality and even once "put the hard word" on the detective.

His vigorous refusal was finally accepted by Onassis with the explanation: "It was meant as a compliment to you, not an insult."

Frank scotches rumours of Onassis' use of heroin and cocaine. "He certainly took pills to sleep and pills to wake up, but that was it."

A big part of Frank's duties was to protect Onassis from the prying eyes and ears of the CIA.

"They didn't like the way he operated - dealing with Arab's, bringing up the price of oil, having his shops built in Japan and keeping out the Americans.

"They even approached me to spy on him. I told Onassis and we fed them false information.

"They tried to use beautiful female agents to infiltrate, but we found out. Onassis would allow them to come to his parties and then deliberately treat them twice as rough as normal, knowing they had to take it or blow their cover. He loved the irony."

Frank concedes that he admired Onassis' "incredible" energy. "He rarely delegated work and his empire was indeed built by him."

His sting with Onassis ended when the magnate decided to return to his former home in Paris and Frank decided to return to Australia. "I didn't see him after that and 18 months later he was dead. But my time with him opened the door for future work with many other powerful people."

Now, Frank is selling up in Sydney and relocating in the U.S. He expects to become a household name there due to the planned Frank Monte movie, the script of which has just been written. "I expect filming to begin next year with a big-name cast."