The library was converted into a new dining room in 1780-81 through the replacement of the bookcases with new Zucchi paintings, the addition of a sideboard in the bowed end, and the filling-in of the windows for niches, the whole painted in green and grey. There is some dispute as to the extent of Adam's work in the conversion of the library into a dining room. To King, there is 'no proof that Adam supervised the conversion but it seems highly likely'. However Harris writes that to consider it an Adam design is 'unthinkable' and Adam was only contacted to design the elements that were beyond the abilities of Stockman.

Bolton considers Adam volume 20/237 to represent a mirror for the old 'eating room' rather than the new dining room. However subsequent scholars have treated it as part of the conversion of the library, an oval design for a mirror rejected when the patron wanted a plain rectangular one. This had happened with the Great Drawing Room (see Adam volume 50/68) and once again Adam had to produce another design. Harris speculates that the rejection in this case was due to the large size of Stockman's already-built tables underneath the mirror position, which would have created an imbalance. Stockman probably also executed the mirror design.