During her visit to California in 1983

Secret files reveal plot to assassinate Queen Elizabeth in the US

Queen Elizabeth revealed before her departure that she had been subjected to several assassination attempts. Archival

Declassified FBI files have revealed a possible plot to assassinate Queen Elizabeth II during her 1983 visit to California.

The potential threat came after a phone call by a man who "claimed his daughter was killed in Northern Ireland by a rubber bullet", according to the document, which also refers to a place frequented by IRA sympathizers.

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

Four years later, militants from the Irish Republican Army opposed British rule in Northern Ireland killed Louis Mountbatten, India's last colonial ruler and Philip's uncle, in a bomb attack.

The document stated that the man claimed that he would have tried to harm the Queen by throwing some objects from the Golden Gate Bridge on the royal yacht Britannia when it passed under the bridge, or would try to kill Queen Elizabeth when she visited Yosemite National Park.

A separate document dated 1989 noted that while the FBI was not aware of any specific threat against the Queen, the possibility of threats against the British monarchy always existed by the IRA.

Queen Elizabeth II died last September at the age of 96 and has previously declared herself the target of several assassination plots.

In 1970, IRA sympathizers made an unsuccessful attempt to derail her train west of Sydney, in 1981, the same organization tried to kill her with a bomb during a visit to Shetland, off the north-east coast of Scotland, the same year a teenager fired a bullet at the Queen's car during a visit to New Zealand, and a teenager fired six bullets during a Royal Guard parade in central London.