The royals tried just about everything to get rid of him short of sending him to the Tower of London. The palace blocked his access to royal engagements, complained to the press watchdog, successfully instructed editors not to use his pictures and even took him to court.
Now aged 77, Bellisario says he has few regrets about his work on the royals, which paved the way for the kind of off-guard, up-close shots beloved of today's celebrity magazines.
"Let's get real -- they love it. Without it, where the hell would they be?" he said.
These days Bellisario, a lifelong socialist, makes frequent trips to Cuba to teach journalism at the University of Havana and, since a spinal condition put him in a wheelchair 27 years ago, campaigns for disability rights.
But, resplendent in a cerise suit, pink shirt and peach tie, he shared some of his exploits with AFP over coffee in London ahead of an auction of his work in September.
Among the estimated 20,000 transparencies is one looking up the queen's dress as she sat by the lake at Sunninghill Park in Windsor with her sister, Princess Margaret, who was wearing a bathing suit.
He had gone searching for Margaret, but was quite surprised when the picture of the queen was exposed in the dark room. "That was purely accidental -- I was absolutely amazed," he says, laughing.
The shots of Margaret prompted the monarch to complain to the Press Council, the then-media watchdog, which in 1964 strongly condemned Bellisario for taking pictures in a private area.
Buckingham Palace had previously taken Bellisario to court for shooting pictures of Princess Anne, the queen's daughter, and he was fined for breaching a local by-law.
Although he was subsequently blacklisted by most British newspapers, Bellisario refused to give up and says he knew foreign publications would always want his work.
The royals' actions were like a red rag to a bull. "It was the worst thing they could have done," he recalls.
He makes no secret of his dislike of the royal family, describing the queen as "that damn woman". "They irritated me first by their presence," he says.
-- From Princess Anne falling off her horse to the Nigerian civil war --
But he had realised that the new monarch -- Elizabeth II took the throne in 1952, around the time Bellisario started working -- was an opportunity to forge a career.
One of his first jobs was at London's Covent Garden, home to the Royal Opera and Royal Ballet, where he borrowed a box to get a good view of the queen's mother across the auditorium.
He had a problem, though. Bellisario was using a new colour film which required his subject to stand still for 15 seconds.
"How did I get it?" he asks. Grinning at the memory, he starts singing: "God, Save Our..." It was the national anthem, for which everyone in the theatre had to stand.
Bellisario insists his pictures are the result of patience and creativity and that he always stayed within the law -- and on the ground. "Never up a tree!" he cries, mock horrified at the idea.
One of his most successful photographs was of Princess Anne falling off her horse in an eventing competition.
He had waited for weeks for the perfect shot, until he caught Anne side-on flying off her horse, her grimacing face in sharp profile.
There was some subterfuge, however -- he used to hide a camera in his baby's pram while out walking in the park -- and of course the long-lens camera was his most useful tool.
Another ground-breaking shot was a grainy picture of the queen and her uncle, the former king Edward VIII, whose abdication had brought shame to the royal family.
Officials denied there was any contact between the pair, but it emerged he was paying daily visits to the Buckingham Palace gardens while undergoing hospital treatment in London.
"Inevitably Mrs Queen was going to come out with her dogs," Bellisario recalls -- and so she did. He photographed the two of them from the 19th floor of the Hilton hotel.
Relations with royals went from bad to worse, particularly with the queen's husband Philip who, according to Fleet Street legend, used to check suits of armour to ensure Bellisario was not inside.
In 1971, Bellisario took Princess Margaret's husband Lord Snowdon to court for what he claims was a deliberate attempt to run him off the road. Snowdon was fined £20 for careless driving.
Eventually, however, he grew tired of the battles and went abroad, covering Northern Ireland, the Western Sahara and the Nigerian civil war.
For a moment, his bravado disappears and his eyes fill with tears as he recalls the endless stream of starving refugee children arriving at Port Harcourt airport in Nigeria.
After all, there is one regret, he says -- "wasting 15, 16 years of my career photographing the royals".
Bellisario's collection will be sold by Omega Auctions in London on September 28. The proceeds will go to his legal advice charity, Reach for Rights.