4, St James's Square SW1

No. 4, St James’s Square is a terraced town mansion dating back to a Barbon townhouse built between 1675 and 1677. It was substantially rebuilt or remodelled in 1726-28 following a fire. Multiple architects have been suggested for the work, including Giacomo Leoni, Nicholas Hawksmoor, and Edward Shepherd. The facade is constructed of amber stock brick with a slate roof. It presents a stately, astylar Palladian design, with a prominent piano nobile. The building has two storeys and an attic, accommodating five windows across the front.

The entrance is located in the second bay from the left, featuring a stone Ionic columned porch, flanched by pilasters and providing access to an eight-panel door topped with a rectangular fanlight. The recessed sash windows are fitted with stone architraves; those on the ground floor are eared with pulvinated friezes and cornices matching the porch's design. First-floor windows have lowered pediments on consoles, while the attic windows have eared architraves at both top and bottom. Horizontal plat bands and sill bands define the ground and first floors. A moulded stone entablature sits above the piano nobile, topped by a secondary cornice and a blocking course for the attic. The low-pitched, hipped slate roof is largely hidden. A stone balcony, added in the early 19th century, adorns the first floor, complete with a simple cast iron railing. Cast iron area railings, featuring urn finials and spear head detailing, further enhance the exterior.

The rear garden front has a four-window main block and a four-window return, lacking dressings, but incorporating a first-floor plat band and sill band, along with an early 19th-century balcony and a crowning entablature with a low parapet. A brick 4-window extension, built in the 19th century, extends from the east wing, mirroring the style of the original building.

The interior is notable for its unusual layout, owing to the site’s northward projection. Key features include a hall with a Baroque chimneypiece and an arcade leading to an inner hall and the stair compartment, which is designed in a Palladian style with some early 20th-century embellishments. Two archivolt arched windows frame a niche containing a plaster replica of Rysbrack’s Chiswick Inigo Jones statue, and the original ceiling exhibits a Jones-Palladian pattern. A spacious stone staircase has fluted column balusters. The first-floor ballroom features Palladian stuccowork to the coved ceiling, augmented by mid-19th century neo-Rococo gilded detailing. A rear drawing room retains its original cornice dado and shutters, redecorated in a mid-19th century French Rococo style, potentially designed by the Earl de Grey, who resided here from 1834 to 1859 and was his own architect and interior designer at Wrest Park. The ground floor rear rooms were redecorated around 1920 by D.P. Milne and P. Phipps, among others.