LONDON Plenty have been over and met British royalty, but Barack Obama and George W. Bush are the only presidents to have ever been invited for a full state visit.
Obama received a royal 41-gun salute at Buckingham Palace on Tuesday to begin a two-day state visit aimed at ensuring the United States and Britain keep the "special" in their relationship.
Bush was given a state visit in November 2003, the first ever granted to a U.S. president, Buckingham Palace officials said at the time.
State visits are formal visits to the United Kingdom by heads of state from overseas, with the aim of strengthening Britain's relationships with other countries, according to the official website of the British monarchy (www.royal.gov.uk)
There are usually two incoming state visits each year. Invitations are sent on the advice of the British government's Foreign and Commonwealth Office. Queen Elizabeth acts as host to the visiting head of state, who stays either at Buckingham Palace, Windsor Castle or, occasionally, the Palace of Holyroodhouse in Edinburgh.
Visits normally begin with a ceremonial welcome attended by the queen and other senior members of the royal family. If the guest is staying at Buckingham Palace, the welcome takes place on Horse Guards Parade.
After inspecting a guard of honor, the visiting president or monarch then travels with the queen in a carriage procession back to Buckingham Palace.
On the evening of the arrival day, the head of state will attend a state banquet in his or her honor.
Before leaving, he or she will occasionally host a banquet or other event to return hospitality at an alternative location.
During the visit, the head of state will meet the British prime minister, government ministers and leaders of the main political parties.
The visiting head of state will also attend a banquet hosted by the Lord Mayor and City of London Corporation, when he or she will meet leaders of commerce and industry.
When heads of state visit Britain less formally, they are nearly always received in audience by the queen.