The dining room would have been located at the back, on the ground or first storey of the house.

The design is a close variant of that designed by Adam in 1766 for Lady Shelburne’s bedchamber at Shelburne House (Adam volume 22/113). The Shelburne House chimneypiece design was inscribed by Adam in pencil with the words, 10t House, Back Parlor, suggesting that Adam had considered reusing it at the Adelphi, although he had perhaps originally intended it elsewhere.

One of the rooms at number 2 Adam Street received a chimneypiece which is a close variant of one designed for the back parlour or dining room for both number 2 Royal Terrace (Adam volume 24/28) and number 9 Adam Street (Adam volume 24/18). The only difference is that the central tablet contains enclosed rather than unenclosed rosettes, and the tazza is supported by foliage rather than a small pedestal. This is identical to the chimneypiece installed in the front drawing room at number 1a Royal Terrace. Both this chimneypiece and its duplicate at number 1a Royal Terrace were photographed by the LCC in 1936-37.