In the early twentieth century, a group of writers and publicists began to talk and write about social hygiene or more commonly known as the theory of eugenics. By this they meant the improvement of the quality of the population by a conscious intervention in the biological laws which governed its growth, development, and reproduction. This discussion led to the foundation of several social hygiene/eugenics organisations: the Eugenics Society, the National Council for Mental Hygiene, the Central Association for Mental Welfare, the People's League of Health, the New Health Society, the National Institute for Industrial Psychology, and several others. First published in 1986, Social Hygiene in Twentieth Century Britain (now with a new preface by the author) suggests that they were linked by a set of interrelated ideas about health and social progress which was influential in the period from the First World War to the aftermath of the Second. Its basic contention is that these groups were influenced by Social Darwinism and that they based their policies on two foundations: the elimination of the unfit and the improvement of the general level of industrial and personal efficiency among the working class. The book offers a critique of Foucault's theory of the development of the sciences of human life, as well as relating the ideas of these groups to the social climate of British life. The social management they envisaged was based on an expectation of deflation and a high level of unemployment. They can thus be seen as throwing light on developments in Conservative policy on 'family life' and the like.