[* "Spring Gardens" was the old (and very cramped) headquarters, near Trafalgar Square, of the Metropolitan Board of Works (MBW, 1855—1889), subsequently used by the London County Council (LCC, 1889—1965). Their [rapacious] parks and open spaces committees were resisted by Commons' activists in favour of local control by a small group [eight] of mainly locally-elected Conservators. But they eventually [recouped/incorporated/absorbed] Wandsworth Common (but not Wimbledon Common & Putney Heath, which is still run by eight Conservators) in 1888/89.
The LCC (from 1963 the Greater London Council (1965—1986) did not move to the new purpose-built County Hall until 1922. This was abandoned just a half-century later when the GLC was abolished by Margaret Thatcher's Government (1986). This is now used (and some would say abused) as a hotel, amusement arcade and aquarium.
Its eventual successor, the Greater London Authority/London Assembly (2000 — now), was based initially at City Hall, a rented office block near Tower Bridge, but moved to the GLC-owned "Crystal" in Canning Town in 2022. This has recently been rebranded "City Hall".
What a way to run a major world city.]
Interesting-looking links
Archiseek: https://www.archiseek.com/2012/1860-metropolitan-board-of-works-london/ Spring Gardens
County Hall Arts: https://www.countyhallarts.com/history History of County Hall