Despite having been on the Labour back benches since 1972 and not part of the shadow cabinet, in 1974, after Harold Wilson's defeat of Edward Heath, Castle became Secretary of State for Health and Social Services. While serving in this position, Castle introduced a wide range of innovative welfare reforms, including the introduction of the mobility allowance, the Invalid Care Allowance (July 1976) for single women and others who give up their jobs to care for severely disabled relatives, the introduction of a non-contributory invalidity pension for disabled persons who had not qualified for invalidity pension, reforms in child allowances, and the linking of most social security benefits to earnings rather than prices.