The drawings for the rear elevations both date to the 1826-7 phase when the windows had been revised. They also show the rear entrance to the vaults. A third example is in the V&A collection (3307.38), which is more elaborate, and shows a double-curved staircase descending into the vaults and elaborate curved stone entrances attached to the rear (see SM 47/5/39, SM 47/5/50). Both are dated to 1827