How Do You Know If the Queen Is at Buckingham Palace?
Queen Elizabeth's presence in a royal residence such as Buckingham Palace will typically be marked by the flying of the Royal Standard flag. The Royal Standard is used to indicate Queen Elizabeth's presence in other contexts, including being flown on automobiles in which she is traveling or private buildings to which she is making an official visit.
Official buildings such as the British Parliament building will also fly the Royal Standard when the queen makes a visit. This flag consists of four quadrants representing the union of England, Scotland and Ireland. The most prominent colors on the flag are red, yellow and blue, with details in white and black.