REPEATED murder threats, often from IRA sympathisers, were made to Queen Elizabeth II, declassified FBI files reveal.

It meant the US service was always on high alert during her US visits.

Before her and Prince Philip’s trip to San Francisco in 1983, one officer revealed a man who often visited a pub “frequented by [IRA] sympathisers” had called threatening to kill the monarch by dropping an object on to the royal yacht from the Golden Gate Bridge.

According to the memo, the officer claimed the suspect wanted to avenge his dead daughter, who was killed in Northern Ireland by a rubber bullet.

It said: “This man additionally claimed that he was going to attempt to harm Queen Elizabeth and would do this either by dropping some object off the Golden Gate Bridge onto the royal yacht Britannia when it sails underneath, or would attempt to kill Queen Elizabeth when she visited Yosemite National Park.”

Before a 1989 royal visit, the FBI said Kentucky police received “several anonymous threatening telephone calls”.

Another memo said: “The possibility of threats against the British monarchy is ever-present from the IRA.”

The 100 pages were released following a freedom of information request.