Queen Elizabeth II faced a potential assassination threat during a 1983 visit to the US, newly released FBI documents show.
The Federal Bureau of Investigation has released a cache of files relating to the late Queen's travels to the US, following her death last year.
They show how the FBI, which helped secure the monarch's safety during her visits, worried about IRA threats.
The assassination threat was made to a police officer in San Francisco.
According to the file, an officer who frequented an Irish pub in San Francisco warned federal agents about a call from a man he had met at the venue.
The officer said the man told him he was seeking revenge for his daughter who "had been killed in Northern Ireland by a rubber bullet".
The threat came on 4 February 1983 - about a month ahead of Queen Elizabeth II and her husband Prince Philip's visit to California.
"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," the document says.
In response to the threat, the Secret Service had planned to "close the walkways on the Golden Gate Bridge as the yacht nears". It is unclear what measures were taken at Yosemite, but the visit went ahead. No details of arrests were published by the FBI.
The 102-page cache was uploaded to the Vault, the FBI's information website, on Monday, following a Freedom of Information Act request submitted by US media outlets.