The location of Room D is shown on MP/CHI0440. None of this set of drawings are dated but the 'Plan of the Garden' is identical to one made in the 1880s for the Marquess of Bute. The Marquess was a tenant at the house from 1881 - 1892 and the plan includes some changes made by him and reversed in 1950. This and the style of the drawings suggests they may date from the late nineteenth century although they could be as late as 1950, but no earlier than 1881.
This is part of the Job: PF/CHI/067 Copies Of Drawings And An Index Showing Chiswick House And Gardens Including Details Of The Chimney Pieces And Sculpture; within the Volume: PF/CHI Chiswick House, Greater London; within the Series: EHC01/022 English Heritage Plans And Measured Drawings; within the Collection: EHC01 English Heritage(Eh):Archive
Source: Historic England Archive
Mantelpiece, Decorative Plasterwork, Hanoverian Villa