Experience and analysis has demonstrated the efficiency and efficacy of incremental housing for and by urban low-income households and communities, supported by, and in partnership with local government. John Turner coined the phrase ‘housing as a verb’ (Turner 1972) to focus attention on the processes by which urban low-income families house themselves, and away from the prevailing preoccupation with housing solely as a product. Yet, four decades later this understanding had still not been absorbed by many national and municipal housing authorities that persisted with ‘conventional’ attitudes to the clearance of ‘slums’ and the unrealisable ambition to replace them with ready-built public housing. As a result urban informal (illegal) settlements in many towns and cities continued to expand (UN-Habitat 2003).