The charitable trust's incumbent is the Publicis-owned Starcom, which won the brief in 2002 from Media Options without a pitch.
Historic Royal Palaces markets the Tower of London, Hampton Court, Kew Palace and the Kensington Palace State Apartments.
The trust currently handles its advertising in-house, with the majority of its media spend concentrated on outdoor work.
Historic Royal Palaces was created in 1989 to manage England's unoccupied royal palaces. The public body is contracted by the culture secretary to manage the palaces on the Queen's behalf.
The organisation has been boosted by TV coverage catering for the public's increased interest in UK history. Approximately three million people visit the attractions every year.
The trust relies on funding from sponsors, donors, members and visitors.