These drawings show Adam's Diocletian wing almost as executed, which was erected in 1769-70, after Adam had made alterations to the interior of the original house. The new wing was built onto pre-existing E-shaped domestic offices to the north-west of the house. It enclosed two courtyards, and provided an additional link to connect the offices to the original house.

The Diocletian wing was so called because it made use of Adam's Spalatro order columns, and vaguely resembled the architecture shown in Adam's the Ruins of the palace of the Emperor Diocletian at Spalatro in Dalmatia. Adam's original Spalatro order capitals were replaced with Corinthian capitals during the nineteenth century.

Adam volume 39/74 shows Adam's intention to include a greenhouse to either side of the principal entrance, as well as a long gallery in the eastern range of the office, and an unusual link to the original house on the south-east corner, with a central circular room in the middle. None of these elements were executed.

The entire domestic offices, including Adam's Diocletian wing, were extensively altered during the nineteenth century. The original house was demolished in 1955 (see scheme notes), and since this time the offices have been used as the principal residence, necessitating various further alterations to the interior.