From the website of the London Gardens Trust:
“Mount Street Gardens (left of image above) are on the site of an important early Georgian cemetery built as a result of the 1711 Fifty New Churches Act. The site was acquired by the newly-formed church of St George’s Hanover Square as a burial ground in 1723. Few burials took place after 1831 and it closed in 1854. Like other urban cemeteries the former burial ground was later converted into a public garden. It was laid out in 1889 with plants, paths and a small fountain designed by Ernest George and Harold Peto. Its name changed to Mount Street Gardens from Mount Field, called after English Civil War fortifications here known as Oliver’s Mount. The layout has little changed since 1889, retaining its late C19th gate piers at one entrance. Around 90 sponsored benches line the paths, almost all of which were donated by Americans due to the proximity of the US Embassy.”
From: Survey of London: Volume 40, the Grosvenor Estate in Mayfair, Part 2 (The Buildings). Originally published by London County Council, London (1980):
“In 1884 the St. George’s Vestry invited designs for their new offices from six architects. From those submitted they selected a scheme entitled ‘Economy B’ by Albert J. Bolton, which after some alterations suggested by the Duke was built in 1857 at a cost of some 15,000 by G. H. and A. Bywater. It was a plainish building with touches of the Queen Anne style.
Far from giving the keynote to the reconstruction of Mount Street, the Vestry Hall was untypical of the ranges of shops with chambers over that were to follow, and of course unique in being built on freehold land…”
“NW CITY OF WESTMINSTER MOUNT STREET, W1 (south side) Nos.87 to 102 – pictured above – (consec.)
From Historic England entry:
Terrace, with return into South Audley Street, of purpose built shops and flats. 1889 to 1895 by Albert J. Bolton. Fine quality red brick and moulded terracotta, slate roofs, in an ornate Franco-Flemish Renaissance style. 3 storeys, gabled attics and lucarnes. Unequal 2 window wide fronts. Ground floor shop front with terracotta, panelled, pilasters. Upper floors have alternate bays set forward and back with 3 or 2+2 light mullioned leaded iron casements, the advanced bays with richly ornamented gables, the set back bays guarded by balustrades above the shop fronts. Between the advanced bays at west end a balustraded balcony and a false balcony supported on an arch across the set back bay. Octagonal corner towers to South Audley Street range. 7 gables to Mount Street, 2 to South Audley Street and one to Chapel Place North return. Prominent terracotta chimney stacks. Part of the late C.19 Grosvenor Estate redevelopment.”