Most books by academics these days owe at least their date of publication to the Research Assessment Exercise. This one, however, would not have existed without it. Since the last RAE I have pursued the theme of this book in a number of articles, but without giving any thought to bringing them together. They could not easily be made into a collection of essays because there is too much overlap between a few of them and in others only some parts were relevant to this particular theme. The RAE requires each member of staff to submit four pieces of work, and it dawned on me that this would allow little scope to indicate that I have been working on the subject of this book, especially if berths were to be found for the fruits of other projects. It is difficult to exaggerate the importance of a successful outcome in the RAE for our institutions and for the continuing viability of our disciplines, so there was nothing else for it but to draw the material together so they could find a home together when it came to identifying four items for assessment. In the end, about half of the book consists of repeats of material that has been published since the last RAE. The opportunity has been taken to expand or contract some sections, correct errors, update references and reduce the number of collateral footnotes, so there is no item that has been reproduced exactly as it first appeared. That is not to say that what follows supersedes the originals. In all but two cases (chapters 4 and 7) the original articles have sections on matters beyond the scope of this book: if you want to find out why I have argued that Cinaed mac Ailpín was a Pict, for example, you will need to look up the article from which most of chapter 3 has been derived; or if you wish to read about the kingdom of Strathclyde, you will need to look at the article from which much of chapter 5 has been extracted. I am very grateful to the editors and publishers of the articles reproduced in chapters 3, 4, 5 and 7 for their very ready cooperation in this, particularly Professor Thomas Owen Clancy, Professor John Gillingham, Professor James Kirk, Dr Pamela O'Neill, Caroline Palmer and Professor David Wright. I am particularly grateful to John Davey of EUP for his encouragement of this project from the outset.