But with time even the city wall became less important as a symbol of wealth, privilege and safety, as technological advances – most notably the invention of gunpowder – made such defences less effective (Keegan 1993). Cities, however, continued to be characterised by defensive features as new walled and gated spaces developed, this time within the city boundaries, as danger was increasingly seen to originate from within, rather than outside, the urban area (Luymes 1997; Atkins et al. 1998). By the mid-nineteenth century many Western cities were characterised
by secure residential estates amidst vast tracts of working class housing, which were seen as terra incognita (Newman 1980; Jackson 1992).