This book has taken a long time in preparation and I owe thanks to many at the British Institute of International and Comparative Law who in the course of discussions and meetings deepened my understanding of the subject. The Leverhulme Foundation generously funded an early part of the research for which I would like to express my gratitude. Alexander Birtles helped me in that initial research, Christopher Harris checked the reference to English cases in the book, Paul Greatorex, the section on procedure in English law, Chanaka Wickremasinghe, the section on immunities of international organizations, and Gary Born very generously gave time to read through and check the section on US law. I would like to express my thanks to all these and particularly to Chester Brown whose diligent sub-editing of the first half of the book in the summer of 2001 spurred me to complete the text for publication. Thanks also to John Louth, Geraldine Mangley, and all at OUP who have carried out the publication of this book. And finally to my family, particularly Matthew, for their encour- agement throughout.