In the course of the many years it has taken to prepare and write this book, I have incurred many debts. Not the least of them is to my editor at Penguin, Simon Winder, who has always been as supportive as he has been patient. I owe a very great deal to the generations of students at Cambridge I have been fortunate enough to teach and learn from. This particular acknowledgement goes well beyond conventional courtesy, for it is only when thinking about what I might say to them, and then improvising it in the lecture-or seminar-room, and seeking to deal with their criticisms, that any worthwhile ideas have come my way. Another activity conducive to creative thought is walking the dog, from home to the Faculty in the morning, out into the fields west of Cambridge at lunchtime and back home in the evening. For that reason, I have included Molly the Dalmatian among the dedicatees of this book. Although usually dozing, she has been present on her favourite armchair in the window-alcove of my office while every word of this book has been written. The Faculty of History has provided me with the ideal working environment, not least because it contains the largest dedicated history library in the country, and is only a couple of minutes away from one of the great libraries of the world, in the shape of the University Library. To the staffs of both libraries, especially Dr Linda Washington of the Seeley Historical Library, I express my warm appreciation. Of the very numerous colleagues, in and outside Cambridge, who have helped me in all sorts of ways, I single out for special thanks Chris Clark, Brendan Simms, Heinz Duchhardt, Charles Blanning, Ivan Valdez Bubnov, Eirwen Nicholson, Emma Griffin, David Brading, Robert Tombs, Robert Evans, Jo Whaley, Roderick Swanston, Martin Randall, Peter Dickson, Simon Dixon, Uwe Puschner, Ulrike Paul, Hagen Schulze, Munro Price, Bill Doyle, Julian Swann, Peter Wilson, Maiken Umbach and Jonathan Steinberg. I owe a special debt to Derek Beales and Hamish Scott, who heroically read my typescript and saved me from many sins of omission and commission. Not long after I began writing, my son Tom was born, to be joined three years later by Lucy. Although their arrival slowed progress appreciably, they also provided the necessary impetus to get me through the sticky periods. I could not have finished at all if my wife, Nicky, had not shouldered most of the burdens of parenthood, leaving me with just the pleasures. So it is right that her name should appear first on the list of dedicatees, just as she is first in my heart.