This doctoral thesis traces the various forms in which ordinary people engaged in the stock market across twentieth-century Britain. It asks how and why previously stigmatised forms of investment and speculation came to be regarded as socially, politically and economically desirable. I argue that financial and economic historians, preoccupied with the growing dominance of financial institutions over British security markets during this period, have neglected the social and cultural relevance of popular share ownership. Consequently investment is seen as more than an economic activity. Understanding the ways in which social and cultural attitudes towards finance relaxed over time, allows us to better understand the arrival of neoliberalism in Britain. After World War I, Britain witnessed a significant expansion of private stock market investment. However, in comparison to the United States, Britain’s financial establishment took a more conservative stance on universal share ownership and restrained much of the potential for a “democratisation of investment”. After 1945, private share ownership continued to grow gradually across classes due to higher living standards and in spite of nationalisation, high taxation and the institutionalisation of securities markets. Politics was not the main driver of this trend as efforts to widen share ownership were difficult to square with the interventionist postwar economic settlement. More importantly, the rapidly expanding trade of financial journalism increasingly educated multiple audiences about stock market affairs. By widening the analytical scope beyond socioeconomic conditions, it becomes apparent that the sweeping social and cultural changes during the 1950s and 1960s helped to loosen older reservations against financial speculation, thereby drawing evermore investors into the market. The key shift of this period was that ‘playing the stock market’ became a popular and socially acceptable hobby, predominantly among middle-class households. Tracing these developments to the 1970s and 1980s, this thesis concludes that market populism had a powerful appeal to savers and investors hit by inflation, thereby accelerating the growth of economic individualism long before the Thatcherite Revolution unfolded in Britain.