This survey plan is in the hand of Still Leadbetter - using his particularly distinctive scale bar - which is especially obvious in his survey plan for Hatchlands. Moreover, there is archival evidence of Leadbetter's involvement. Worsley notes that Leadbetter wrote to Drake in February 1761 that he had 'delivered plans of your best rooms to Mr Adams about the middle of last month and as soon as he has made designs for the ceilings & c (which you approve) I will immediately send as many plasterers as can be employed.' This contradicts Tait's statement that this drawing is by Robert Adam and 'in this simple clear style of the Scottish office'.
Adam's pencil annotations to this survey plan show the portico which was executed to designs by Adam, and two projecting bays which were not.