Britain’s Queen Elizabeth II visited the United States in 1983, when she was assassinated. After 40 years, the United States’ intelligence agency, the Federal Bureau of Investigation (FBI), has revealed such information in some documents. BBC news
These documents show that the FBI, which was responsible for the security of the royal family, was very concerned about the threat received from the Irish Republican Army (IRA). The assassination threat came to a San Francisco police officer. A man told him that he would kill the queen.
The man claimed his daughter was killed by rubber bullets fired by police in Northern Ireland. He plans to remove the queen to take revenge. The planner even told how to kill. He warned the detectives about this.
In view of this threat, the Secret Service closed the Golden Gate Bridge walkway as the yacht approached. And what arrangements were made in Yosemite Park, of course, is not clear, but the Queen visited there.