By 1935 housing policy had moved beyond the health of towns question and sanitary reform. The legislation of the 1920s had added exchequer subsidies to the powers of local authorities to build houses. The intention to build 'homes fit for heroes', the threat of civil unrest, shortages of labour and high construction costs had led to major innovations in policy and a major public investment in housing. The Housing (Financial Provisions) Act 1924 in particular had 'estabished the local authorities as part of the permanent machinery for providing working-class houses' (Bowley, 1945, p.40). By 1935 some 950,000 local authority dwellings had been built in Great Britain. Substantial reconditioning of dwellings had also had an impact on housing conditions, and Bowley (1945, p. 147) suggested some 300,000 houses had been made fit for human habitation through such activity in each year between 1919 and 1930. Slum clearance was beginning to expand following the Housing Act 1930.