Directly underneath the State Apartments is a suite of slightly less grand rooms known as the semi-state apartments. Opening from the Marble Hall, these rooms are used for less formal entertaining, such as luncheon parties and private audiences. Some of the rooms are named and decorated for particular visitors, such as the 1844 Room, decorated in that year for the State visit of Tsar Nicholas I of Russia, and, on the other side of the Bow Room, the 1855 Room, in honour of the visit of Emperor Napoleon III of France. At the centre of this suite is the Bow Room, through which thousands of guests pass annually to the Queen's Garden Parties in the Gardens. The Queen and Prince Philip use a smaller suite of rooms in the north wing.

Which rooms are used for less formal entertaining such as luncheons or private audiences?