While at it, I tried to identify the layout of the rooms occupied by the Royal Academy.
First, the staircase:-
The first room on the first floor opening out onto the staircase was the Ante Room and Library, with surprisingly elegant plasterwork decoration and Theory by Reynolds in the middle of the ceiling:-
The room next door over the arch was the meeting room, described as for the Royal Society, with chimneypieces by Joseph Wilton:-
To the left was a room for casts with the original insignia of the RA in the plasterwork decoration:-
Beyond, in the centre of the Strand façade, the original Council and General Assembly Room, a good space, again with chimneypieces by Wilton:-
The rooms of the Royal Academy interleaved with those of the Royal Society.
On the floor above was the Great Room, due to be restored as part of the plans by Witherford Watson Mann.