All right Capetonian, perhaps a little strong on my part but might I please subsitute perhaps the word ghetto for slum. The dogs, razor wire, armed security guards, high walls, alarm systems and the third eye between the shoulder blades probably do make some areas of Johannesburg safer than certain strangely related parts of London.
In the elder days before the coming of the Prester there used to be a great hotel in Johannesburg called the Carlton. Sol Kerzner made his debut there as a sort of strong arm fixer at a nightclub called Raffles in the hotel. Sad to relate that the place looks today as though it'd been used for tank target practice. That's perhaps why all the hotels have moved out of Johannesburg into Rosebank, Hyde Park and Sandton.