Construction began in 1784; when these rooms were visited in September 1785 by the usually critical Horace Walpole, he was impressed, writing that when completed, Carlton House would be "the most perfect in Europe".
"There is an August simplicity that astonished me. You cannot call it magnificent; it is the taste and propriety that strike. Every ornament is at a proper distance, and not one too large, but all delicate and new, with more freedom and variety than Greek ornaments; and, though probably borrowed from the Hotel de Condé and other new Palaces, not one that is not rather classic than French."
When completed, Carlton House was approximately 202' long, and 130' deep. Visitors entered the house through a hexastyle portico of Corinthian columns that led to a foyer that was flanked on either side by anterooms. Carlton House was unusual in that the visitor entered the house on the main floor. (Most London mansions and palaces of the time followed the Palladian architectural concept of a low ground floor (or rustic) with the principal floor above.) From the foyer, the visitor entered the two story top lit entrance hall that was decorated with Ionic columns of yellow marble scagliola. Beyond the hall was an octagonal room that was also top lit. The octagonal room was flanked on the right by the grand staircase and flanked on the left by a courtyard, while straight ahead was the main anteroom. Once in the anteroom, the visitor either turned left into the private apartments of the Prince of Wales, or turned right into the formal reception rooms: Throne Room, Drawing room, Music Room, Dining Room.