I went to a party in a building very close to that one, it overlooked Hyde Park and the roundabout at end of Park Lane/Edgeware Road. This was in 1969 and a girl I know was attending the Lucy Clayton Modelling School and a girl she met there, a fellow student, invited her to a party 'at Mummy & Daddy's place' and to bring a few friends.
So a bunch of council estate yobs rubbed shoulders with a bunch of young hoorays, twas quite an extrordinary experience.
And back in 72/73 I used to deliver smoked salmon to elderly jewish ladies living in Hyde Park Mansions, as well as the Royal Opera House, amongst others.