21, Upper Grosvenor Street W1

This is a terraced town house located on Upper Grosvenor Street in London, originally built in 1732. It was significantly altered and refronted between 1908 and 1909 by Ralph Knott and E. Stone Collins. The exterior is Portland stone with a slate roof, and showcases an inventive refronting with subtle references to Central European Baroque architecture.

The house is four storeys high, with a basement and dormered mansard roof. It is three windows wide, with rusticated quoins on the flanking sides of the front. The ground floor is channelled, with an elliptical arched doorway on the right, positioned below a porch formed by a bowed projection of the first-floor balcony. The balcony is supported by a pair of Doric columns with small platforms (dosserets). The ground floor has plain plate glass casement windows. The first floor features French windows within architraves, each with a large keystone rising into a heavy segmental pediment. The apron of the second-floor windows rises from these pediments, creating a unified composition with the bolection architraves of the second floor, which have carved scrolled supports. This arrangement leaves an empty space below the high-set, circular (oeil-de-boeuf) windows on the second floor, each also featuring a keystone. A cornice, supported by four carved consoles, runs along the top of the front, above which is a parapet with coping and a pedimented dormer. The ironwork on the first-floor balcony is articulated by squat stone obelisk supports. Elaborate wrought iron standards decorate the area railings.

The interior, which dates from the Edwardian period, is in a neo-Georgian and French style, with wood panelling (boiseries) in an L-shaped drawing room. The building represents a rare example of domestic work by the architects of County Hall.