The letter, sent to then-President Ronald Reagan to thank him for an overseas visit, is among a bundle of previously secret documents only available in the US. Sent from Big Horn, Wyoming, and signed Elizabeth R, it informs him that she had spent "a glorious week's holiday doing the things I like best - looking at thoroughbreds, and walking in the wide open spaces by the mountains".
The letter was obtained by the Campaign for Freedom of Information, as the Government outlines its plans in a White Paper for less secrecy in future.
Buckingham Palace has asked that royal secrets in government archives remain hidden but this has been rejected, though bank statements and other personal matters will be exempt.
The US documents demonstrate a less than deferential tone among diplomatic personnel. A memorandum from the American Ambassador to Algiers notes that "Prince Phillip" [sic] will visit "in his capacity as chairman of some international equestrian federation whose exact name I did not get".
He adds: "Action Rabat: please urgently ship to Algiers all available diamond tiaras normally worn by embassy Rabat wives when received by your royalty."
Documents from 1940 reveal the FBI trailing royalty, in this case the then Duchess of Windsor. A memo says: "I noticed that the Duchess was reported as being violently pro-German; on a subsequent date I noticed that her clothes were sent to New York City for dry cleaning. The possibility arises that the transferring of messages through the clothes may be taking place."Reuse content