I am grateful to the staff of the Manuscripts Room at Cambridge University Library for access to the Butterfield papers in their care, to Sophia Lambert for the loan of Margaret Lambert’s papers, and to Chris Calladine for sharing his memories of Herbert Butterfield. Gill Bennett, Michael Bentley, Philip Carter, Jim Daly, Keith Hamilton, David Hayton, Sara Hiorns, Michael Kennedy, Colin Kidd and Denis Smyth have all made valuable comments on earlier versions of this book.
I also wish to thank Philip Carter and Philip Murphy for accepting this book for inclusion in the IHR Shorts series, and Robert Davies, Lauren De’Ath and Jamie Bowman for their help in preparing it for publication.
Although I am an employee of HM Government, none of what I have written should be taken as an expression of official policy.