LONDON: 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 that also refers to a bar frequented by Irish Republican Army (IRA) sympathisers.

The queen and her husband Prince Philip visited the west coast of the United States in February and March 1983, and the trip passed off 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 was going to 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.