Two flats built 1862-3 as part of three back-to-back blocks, which are now London's oldest remaining mansion flats.  It was social anathema to early and middle Victorians to share facilities such as front doors, hallways and staircases and it took another twenty years for this continental and Scottish idea to become fashionable.  The flats attracted MPs, actors, doctors, lawyers, army and naval officers, with a strong ex-colonial tendency.  From the 1930s the area has been very strongly associated with secret intelligence agencies, with many of the people working there living nearby, certainly the case with one of the flats.