A business history of the Royal Mail Steam Packet Company (later Royal Mail Lines), which from 1851 provided a mail service between Britain and South America. The author explores the wider political and economic context, covers the development of Argentina and Brazil as trading nations, and changes in ship design leading to the development of greater cargo capacities. He also looks at the importance of the refrigerated meat trade and the growth of passenger services. Facing the challenges of international competition, air travel and containerisation, the company ran into serious financial difficulties and was finally acquired by Furness, Withy & Co in 1965. Tables chart the changing trade conditions and financial position of the company. A fleet list covering the period 1851-1965 is included.