A former police officer has revealed Queen Elizabeth II was a victim of an assassination attempt.

Retired Dunedin detective Tom Lewis said the Queen was almost murdered by 17-year-old Christopher John Lewis in Dunedin, New Zealand during a diplomatic trip in 1981.

According to the Independent, Lewis fired a .22 rifle at the monarch when she stepped out of her royal motorcade to greet a roaring crowd.

The bullet had narrowly missed the Queen's head, and while the audience had reportedly heard the gunshot, authorities maintained at the time it was the sound of a council sign falling over.

"You will never get a true file on that, it was reactivated, regurgitated, bits pulled off it, other false bits put on it," Tom said. "They were in damage control so many times."

Lewis said the New Zealand government had covered up the assassination attempt in fear she would boycott the country and cause deep embarrassment, Daily Mail reported.

The police failed to charge the teenager with treason - which if found guilty, would have made him eligible for the death penalty - because they had received an order from "up top."

Murray Hanan, Christopher's former lawyer said: "The fact an attempted assassination of the Queen had taken place in New Zealand... it was too politically hot to handle. I think the government took the view that he is a bit nutty and has had a hard upbringing, so it won't be too harsh."

Christopher later claimed in his unpublished autobiography that he had been told in interrogation to never speak about the event. He said the police had threatened him should he not follow their orders.

"If I was ever to mention the events surrounding my interviews of the organisation ... they would make sure I 'suffered a fate worse than death,'" he wrote.

Christopher was later charged with possession of a firearm in a public place and discharging it, a significant downgrade from treason.

However, this wouldn't be the attempted murderer's only brush with the law.

In one of Christopher's several interrogation sessions, he told authorities he had been ordered to kill Queen Elizabeth II by a mysterious Englishman called the "Snowman."

The Snowman had allegedly told Christopher about the far right groups in the U.K. - like the National Front - and said he could take refuge in similar groups in new Zealand if he were to successfully assassinate the Queen.

Christopher would later be jailed for three years, but was transferred to a psychiatric hospital in 1983. In the same year, he would attempt to break out of his psychiatric ward in an effort to assassinate Prince Charles, who traveled with Princess Diana and a young Prince William, during an official visit.

He wouldn't let his obsession with the royals go, which forced the police to send him away on a taxpayer funded holiday to the north of the country - to avoid a potential run in with the monarch during her 1995 New Zealand tour.

In 1997, Lewis committed suicide in prison while awaiting trial for the murder of a young mother and the kidnapping of her child. He was 33-years-old.

Did you ever hear about the 1981 assassination attempt?