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Although not suggested before, an identification as Syon seems plausible as this building has a similar long, flat front and corner towers. See also the view through trees on folio 12 (D05507) and another on folio 35 of the sketchbook (D05543). On the other hand, Hill suggests that a sketch on folio 27 verso (D40570) of a statue in a niche at the corner of a building shows the same ‘Italianate villa’.1
Hill 1993, p.161.