This study considers how examining the Popular Front movement against fascism in Britain sheds new light on thirties leftist fiction. It brings into view a range of critically neglected texts, focusing on the work of John Sommerfield, Arthur Calder-Marshall, Jack Lindsay, Lewis Jones and James Barke. The thesis shows how their fiction relates to and participates in a mobilisation of cultural forces against fascism both at home and abroad. The thesis is divided into three parts. Part One, ‘Realism and Modernism’ begins by examining how British writers negotiated the respective claims of the developing Soviet aesthetic of socialist realism, the mobilisation of European intellectuals against fascism and the heritage of literary modernism (chapter one). These currents of thought are then explored through readings of John Sommerfield’s May Day (chapter two) and Arthur Calder-Marshall’s Pie in the Sky (chapter three). Part Two, ‘On English History’, discusses leftist writings of the history of England under the rubric of anti-fascism; at its heart is a reading of Jack Lindsay’s trilogy of English historical novels (chapter four). Part Three, ‘Class, Nation, People’, first examines the ‘national’ turn in Communist politics as it was negotiated in the work of the Scottish novelist James Barke (chapter five), before turning to the fiction of the Welsh proletarian novelist Lewis Jones (chapter six). In both We Live and The Land of the Leal, the Spanish Civil War plays a key role in mediating the relationship between working-class historical experience and the demands of internationalist anti-fascism. The chief contributions are firstly a recovery and critical reconsideration of a range of marginalised works, and secondly a demonstration of how these novels can be read in terms of a radicalised and populist realist aesthetic, consonant with and interpretable in terms of the work of Georg Lukács in the 1930s.