No.18 and Attached Railings

No. 18 is a house, later converted into flats, dating to circa 1790-1793, with alterations made in the 19th and 20th centuries. It was designed by John Palmer. The front of the building is faced with limestone ashlar, while the rear is a mix of limestone ashlar and rubble. It features a mansard roof covered with Welsh slate, a coped gable wall to the left with a brick and ashlar stack, incorporating early clay pots, and brick and ashlar to the front and rear roofs.

The house is three storeys with an attic and basement, and has a three-window facade. The first floor has three six/nine-pane sash windows with wrought iron balconettes. The second floor has three six/six-pane sash windows. The ground floor features two six/six-pane sash windows to the left, and a six-panel door with a fanlight over, set within a plain reveal and accessed by a step to a pennant paved crossover with a cast iron footscraper. A 20th-century six/six-pane sash window and a half-glazed door are located in the basement, with a 20th-century extension providing access from the area of No. 17 Park Street. There are a double and a single dormer with plate glass sashes. Architectural details include a band course over the ground floor which serves as the sill band for the first floor windows, a further sill band to the second floor, a frieze and a moulded eaves cornice, and a coped parapet ramped down to the centre. The rear elevation largely retains its original sash windows, including those with wrought iron balconettes, and incorporates a double dormer and a 20th-century rooflight, alongside a small reconstituted Bath stone extension. The interior has not been inspected.

Wrought iron railings with shaped tops and limestone bases are present. The house was part of an incomplete development of St James's Square, constructed on land leased in 1790. The upper part of Park Street was designed by John Palmer, and subsequently continued by John Pinch after 1808, though the intended continuation as Regent Place was never realised. Associated historical documents include an abstract of title from 1856.