In 1971, when working on Empire trade and migration between 1917 and 1939, I collected the first of the archival materials that I later worked into the fabric of this book. Other materials were added as time permitted. My researches were assisted by two Canada Council travel grants, a Canada Council Leave Fellowship, a visiting professorship in the University of Edinburgh, and a year's association with the Institute of Commonwealth Studies, University of London. All this assistance is most gratefully acknowledged. I must also thank archivists and librarians in the Public Record Office (London), the Public Archives of Canada (Ottawa), the Roosevelt Library (Hyde Park), and the South African State Archives (Pretoria), as well as university librarians at Toronto, London, Cambridge, Edinburgh, Birmingham, Cape Town, and the Witwatersrand. Among those who have helped by commenting or discussing, or who have read sections of the manuscript, I must mention in particular Robert Boyce, David Dilks, Malcolm Knight, Donald Moggridge, Susan Howson, Leslie Pressnell, Brian Tomlinson, and G. H. de Kock. Sections of the book have been presented, usually in draft or preliminary form, to the Economic History Workshop in the University of Toronto, to the Monetary History Group in London, and to university seminars in Edinburgh, Hull, Exeter, Swansea, Leeds, Cape Town, and the Witwatersrand. I have learned a great deal from the comments, questions, and suggestions of the participants in these gatherings.