The Federal Bureau of Investigation (FBI) revealed a file about a possible plot to kill Queen Elizabeth II in 1983 during her visit to the US by a potential sympathizer of the Irish Republican Army.

A newly released cache of FBI files has revealed a potential plot to assassinate Queen Elizabeth II during her 1983 visit to California.

The possible threat followed a phone call made by “a man who claimed that his daughter had been killed in Northern Ireland by a rubber bullet,” according to the document, referring to a bar frequented by Irish Republican Army (IRA) sympathizers.

The queen and her husband, Prince Philip, visited the west coast of the United States in February and March 1983, and the trip passed without incident.

Four years earlier, in 1979, IRA paramilitaries opposed to British rule in Northern Ireland killed Louis Mountbatten, the last colonial governor of India and an uncle of Philip, in a bomb attack.

The file states that the man claimed he would attempt to harm the queen “by dropping some object off the Golden Gate Bridge onto the royal yacht Britannia when it sails underneath.”

Alternatively, he “would attempt to kill Queen Elizabeth when she visited Yosemite National Park,” they added.

A separate file among the documents, dated 1989, pointed out that the FBI was unaware of any specific threats against the queen.

The queen, who died last September at the age of 96, has previously been reported to have been the target of other assassination plots on around 5 occasions.

Miroslava Salazar with AFP