Thomas Tompion's sundial at the Bath Pump Rooms.  BSS Register SRN 2492.

The dial was lost until 1971.  Dial is octagonal of side (approx) 355mm across flats. Triangular sheet gnomon with scalloped back edge. Four gnomon supports.
N-S line bisects the sides.

The clock is an exceptional and very rare Tompion equation clock which is housed in an unusual case inset into the wall for security. More info Here