23, Upper Brook Street W1

No. 23 Upper Brook Street is a terraced town house built around 1742, with internal alterations from the late 18th century and a rear extension added in 1808. The building features a stucco exterior with stone dressings and a porch that was added by Thomas Cundy II in 1865. It is constructed of brown brick with a rusticated stucco ground floor and has a slate roof. The house stands three storeys tall, with a basement and a dormered mansard, and is three windows wide.

To the right, there is an enclosed Doric porch that includes a lunette fanlight doorway and altered wing lights, topped with a balustraded parapet. The windows are recessed with flat arches, while the first floor features French casements with cornices supported by consoles. The second floor windows have architrave surrounds. The building has a cornice and parapet, with dormers that have pediments on consoles. The centre and left first floor windows are adorned with stone balconettes and early 20th-century ironwork. Cast iron area railings are also present.

Inside, the house retains several original features, including a central top-lit staircase flanked by closets that serve the front and back rooms. Many rooms still have 1740s panelling with moulded dentil cornices. The hall opens through an archway onto the staircase, which has stone treads with chamfered soffits and a lyre pattern iron balustrade. The circular skylight drum, dating from the late 18th century, is decorated with paterae and festoons, while early 19th-century mouldings can be found in the 1808 rear extension.