The thesis establishes the main economic and structural changes in the food industries between the wars and assesses the part played by convenience foods in that process. It first reviews and presents data from the Census of Production 1907-1948, to show growth rates and the main structural changes. These include an increase in concentration, the emergence of new trades based on product and process innovations, tbe creation of brands and the entry of multinationals into UK food markets. Associated changes in food consumption and food distribution are also reviewed. The body of the thesis examines the impact of convenience foods on the food industry. An account of 'convenience' and a taxonomy of convenience foods is presented (which is critical of the AFS view) based on Census of Production data. It is shown that convenience foods expanded their share of food industry output and had many of the characteristics of the 'new industries' which were an important feature of British industrial development in the period. The central issue, which occupies the remainder of the thesis, is how these foods were produced and marketed and the forms of competitive behaviour which explain the penetration of the new foods through markets. A model of competition developed by M. E. Porter is used as a framework for the exploration of these questions. He adopts the analytical concepts of new entrants, substitutes, the power of suppliers and buyers and competitive rivalry between incumbent firms in markets. These concepts are examined and illustrated with empirical data drawn from company archives relating to the marketing operations of firms such as Kellogg's, Rowntree's and Horlick's. A detailed account of high speed canning illustrates the economic development of the industry over two decades. The thesis concludes that convenience foods had a significant impact on the food manufacturing industries between the ware.