Ptolemy Dean notes that 'This building stood on the north side of the Strand, at the corner of Agar Street, now Zimbabwe House.' (P.Dean, Sir John Soane and London, 2006, p.232). The corner site gave the building the advantage of windows on the long 56 feet 10 inches side elevation and drawing  shows a bowed window over a side entrance that leads to a stair (open-well with quarter-pace landings). Perhaps the building was to be divided across the middle of the long side? There are no windows to the back elevation but a court gives light to the stair and to a back room that also has a single window in the flank wall.
Sir John Soane's collection includes some 30,000 architectural, design and topographical drawings which is a very important resource for scholars worldwide. His was the first architect’s collection to attempt to preserve the best in design for the architectural profession in the future, and it did so by assembling as exemplars surviving drawings by great Renaissance masters and by the leading architects in Britain in the 17th and 18th centuries and his near contemporaries such as Sir William Chambers, Robert Adam and George Dance the Younger. These drawings sit side by side with 9,000 drawings in Soane’s own hand or those of the pupils in his office, covering his early work as a student, his time in Italy and the drawings produced in the course of his architectural practice from 1780 until the 1830s.
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Contents of London: 429 Strand, survey for the Westminster Life Insurance Office, 1795 (4)
-  Survey drawing: ground floor
-  Survey drawing: first floor (NO IMAGE)
-  Survey drawing: second floor
-  Survey drawing: third floor