History does not record what his lovers thought of the attack. But tourists admiring the Danish national symbol can now not be sure whether the mermaid is looking over her shoulder for a prince or an assailant.
Jorgen Nash's attack has been followed by many more acts of vandalism against Edward Eriksen's 1913 bronze statue. But all Mr Nash wanted to do was to let off steam, he said in his 1997 confession. "At the start of the Sixties I had two wives at the same time," said the eccentric, 78-year-old artist. "One of them was a 20-year-old student of mine. When I returned from a tour of Norway in April 1964, this young love of my life had been thrown out by my older wife, who was terribly jealous."
In his anger, he bought a hacksaw and cut the bronze lady's neck. "I was in luck that night," he recalls. "It was awfully cold, so the seafront wasn't crowded with the usual lovers and drunks. And the hammering from the docks created a cover for my sawing noise."
It took five broken blades before the head finally came off. It has never been recovered from the shallow grave near Copenhagen where Mr Nash dumped it.
The event sparked anger and sorrow among the Danes, who regard the little mermaid as their Statue of Liberty.
Ten thousand newspaper articles and 100 television and radio programmes covered the story. It was also front-page news as far away as Moscow and Tokyo.
So much attention was given to the mermaid murder that since 1964 more than 200 people have admitted to the crime, demanding conviction and fame. Among them was a radical feminist group that claimed the mermaid was an insult to the female sex and therefore deserved the harshest treatment.
"Last year I was promoting my book at an exhibition and a policeman came up to me," Mr Nash said this week. "He told me that on that day eight people had tried to enter the exhibition, claiming they beheaded the mermaid and wanting to punish me for taking the credit. Unbelievable."
Never one to let pass an opportunity for attention, Mr Nash is in the process of arranging a party for wannabe decapitators. "I plan to gather them all, find 200 divers to search for the head in the marsh and have a grand celebration." The bizarre party would be timed to coincide with the publication of his second volume of memoirs.
There have been several copycat attacks on the statue. In 1976, it was covered in red paint and eight years later she lost her right arm to two drunk men, who humbly returned it to the police the following day.
And in 1990, someone tried to cut off her head again, but had either too weak a saw or too weak a will; the villain only made it half-way through the neck and the mermaid was able to gaze at the sea in peace for another eight years before a more successful killing took place. That was discovered in the early hours of 8 January last year by a television cameraman, Mich- ael Forsmark Poulsen. "I was called up at 3.30am by a youngster who said that the mermaid was `missing something'," Mr Poulsen said. "So I went out to the waterfront just in time to film two people wearing balaclavas rollerskating away from the mermaid, who was headless once again."
A television station offered a reward for the recovery of the maiden's head but it was returned anonymously. Mr Poulsen was later questioned by the police, suspected of being involved in the crime. "I do have a record of theft and vandalism," he admits, "but I swear I did not murder the mermaid."
But in Denmark, nothing is a bad as a mermaid murder and Mr Nash is the only decapitator who has faced national vilification - even if it was 30 years after the event. Able to escape prosecution because the case was old, Mr Nash holds the doubtful honour of being the founder of a culture of national symbol vandalism.
Neither Big Ben nor the Statue of Liberty has endured what the peaceful little mermaid has suffered while awaiting her prince.