As ever, much gratitude in general to the Bletchley Park Trust, whose work in ensuring that the codebreakers are at last properly celebrated goes from strength to strength. For information on visiting the wonderfully restored Bletchley Park Museum, visit www.bletchleypark.org.uk. Thanks also to Professor Richard J Aldrich of the University of Warwick who for some years has been leading the way with his brilliant and wide-ranging studies of GCHQ and global security. In terms of the book itself, I am particularly grateful to Jennifer Barr and Richard Green, both in terms of expert editorial judgements and also terrific enthusiasm. The same also to editor Philip Parker, who came at the manuscript with eagle-eyed flair and impressive knowledge. Many thanks are also due to Daniela Rogers for finding such striking images, Catherine Rubenstein for her laser-beam proof reading and not least to Katherine Josselyn, for sharp and clever ways of ensuring that the world is alerted to the book.