Miasmas and morals
These conditions caused considerable alarm to the more affluent members of society - and not simply from a charitable concern for the social conditions of the poor. The warren of streets posed a threat to public order, allowing criminals to escape observation in the 'rookeries' described by Charles Dickens in Oliver Twist, and it was clear that the streets should be opened up to observation by the police and sanitary inspectors.
'What was needed was through ventilation, the provision of parks to act as "lungs" for the cities ...'
The lack of through ventilation, the putrefaction and stench, was also a threat to public health. Until the general acceptance of the germ theory of disease in the later 19th century, fevers and epidemics were explained by 'miasmas', exhalations from decaying matter which poisoned the air. Hence the alarm of the 'Great Stink'. What was needed was through ventilation, the provision of parks to act as 'lungs' for the cities, and a general process of cleansing.
The need for observation and ventilation meant opening up the city, improving the process of circulation much as an individual's health depended on the circulation of blood and oxygen. One answer was to demolish slums, by driving railways to the new stations or building new roads to allow the passage of traffic. Hence the decision to build Shaftesbury Avenue in London's West End, cutting through some of the worse slums of Soho.
Little was done for the wretchedly poor people who lost their housing during the process, and they were obliged to huddle ever closer in the next block of housing. Some charities - most famously the Peabody Trust in London - built new model housing on the cleared land, but to little avail. The new housing often consisted of grim, forbidding, barrack blocks, and rents were high, so the poor could not afford to live in them. At the end of the 19th century, however, some local authorities did start to build council housing, which offered a new solution to the problem of housing the poor.