IRA Sympathizer Threatened to Assassinate Queen Elizabeth II During 1983 U.S. Visit, According to FBI Records

The FBI investigated a threat from a man claiming his daughter was killed in Northern Ireland who planned to harm Queen Elizabeth II during her 1983 visit to California.
The man proposed dropping an object onto the royal yacht Britannia from the Golden Gate Bridge or killing the queen during her visit to Yosemite National Park.
The Secret Service took the threat seriously and planned to close the walkways of the Golden Gate Bridge when the yacht passed under it.
Queen Elizabeth II completed her visit to the U.S. in 1983 without any incidents related to the threat.
The FBI documents also describe security concerns for the queen's other visits to the U.S. in the late 20th century, including possible threats from the Irish Republican Army.