This book was written while I was on sabbatical leave from the National University of Singapore. I thank the Vice-Chancellor, the Council and Dean of the Faculty of Law for the generous terms on which I was granted the leave.

I spent the sabbatical year as a Visiting Fellow at the Research Centre for International Law of the University of Cambridge. I thank Eli Lauterpacht, the Director of the Centre, for many acts of kindness in making this year a happy and productive one.

I am grateful to Professor James Crawford, Whewell Professor of International Law at Cambridge, who read and commented on an early draft of this work, to Professor Detlev Vagts, Bemis Professor of International Law at Harvard, who enabled me to spend a month of research at the Harvard Law School and to Robin Pirrie, Fellow of Hughes Hall, Cambridge, who was helpful with his advice. I remain responsible for any errors and omissions.

As always, Thanga has been an unfailing source of strength. Ahila, Ramanan and Vaishnavi have given up time that should have been theirs.