the urban environment, the palimpsests through which the traces of earlier structures and ways of living are evident and the contradictions – faultlines – that give all contemporary cities their creativity, vibrancy, uncertainty and senses of danger. This context of urban faultlines is well expressed in Friedrich Engels' first impressions of Manchester in December 1842 when he arrived, aged 22, as an understudy at the Salford mill owned by his father. "The town itself", he wrote, "is peculiarly built, so that a person may live in it for years, and go in and out daily without coming into contact with a working-people's quarter or even with workers, that is, so long as he confines himself to his business or to pleasure walks". Engels attributed this to the combination of "unconscious tacit agreement" and "outspoken conscious determination" to keep separate the parts of the city intended for middle class use, from the areas reserved for working class housing.