The focus of this thesis is Cumbernauld New Town, designated in 1955, and widely considered revolutionary in concept and built form, both by many contemporary architectural/planning commentators and by subsequent historians. It was hailed by its advocates as the first significant built response to the widespread criticisms of early post-war town planning, within early 1950s architectural debates in Britain: the first new towns, especially, had been branded monotonous, low-density housing estates with monofunctional centres, and Cumbernauld would rectify these faults with a dynamic, densely mixed new formula. The thesis examines the development of Cumbernauld from designation in 1955 to the late 1970s, when the final form of the town was settled. Through in-depth research into primary sources, extensive interviews and a comprehensive field-survey of the entire original new town, it assesses whether the picture of a sharp rupture within post-war UK modernism, with Cumbernauld in the vanguard of change, might be simplified or misleading. It concludes that the concept and realisation of Cumbernauld was indeed an incremental development of, rather than revolutionary rupture from, the patterns of its predecessors, and that it drew heavily on a range of mainstream contemporary architecture and planning influences of the late 1950s and 1960s.