46, Grosvenor Street W1

No. 46 Grosvenor Street is a large mansion built in 1910 by architects Blow and Billerey. It involved refacing and restructuring a pair of mid-18th century houses. The building is constructed of Portland stone with a slate roof and showcases a rather heavy interpretation of 18th-century French style. It stands four storeys tall with a basement, and the top floor features a mansard attic.

The façade has three widely spaced window bays. The ground floor is characterized by deeply modelled rustication and three large semi-circular arched openings, each adorned with carved head keystones. The windows on the piano nobile and second floor are framed with architraves, while those on the first floor include balustrades integrated into a dentilled and enriched plat band, with pediments supported by consoles above. The area wall is also stone balustraded.

The rear of the building, facing the garden, has a more dynamic design with five bays, where the central three are advanced. The first floor windows of the recessed bays are framed by pedimented aedicules. Inside, the mansion retains highly ornate and stylistically eclectic decoration, featuring salvaged European medieval and Renaissance elements that have been skillfully combined. Notable interior spaces include the entrance hall and staircases, as well as a grand late Louis XV style music room or ballroom on the first floor, which boasts gilded boiseries and a frescoed ceiling, likely created by Maurice Tastemain for Billerey.