[v] The scope and limitations of the essay which follows are set out in its first chapter. Of its shortcomings it will be for others to speak. I am sensible that it has many. There would have been more had it not been for the assistance and advice which have been so generously offered to me at every stage of the enterprise.

I am grateful to the Consejo Superior de Investigaciones Cientificas for the grant of a scholarship in the academic year 1966-7, to the University of Oxford for awarding me the Duque de Osma Studentship in 1968, and to the University of York for contributing to my expenses in Spain in 1972.

The thesis upon which the present book is based was supervised by Miss E.S. Procter, and I owe much to her watchful criticism, especially where legal and institutional matters are concerned. I hope that I have also profited from the criticisms of my examiners, Professor P.E. Russell and Dr. P. Chaplais. I also received much useful advice at an early stage from Dr. (now Professor) D.W. Lomax.

I was happily enabled to benefit from the experienced counsel of Dr. P.A. Linehan, who had completed a viaje de investigación round the cathedral archives shortly before I began my own; with these practical matters, as with others, his help was invaluable. Professor Russell furnished me with an introduction which made my visit to Avila agreeable as well as profitable. In Spain it is however to Don Antonio García y García, of the Universidad Pontificia de Salamanca, that I am most deeply indebted: he supplied me with introductions to all the ecclesiastical archives of his native Galicia; he unstintingly lent me books from his own library, and brought to my notice others of which I would have remained ignorant; he plied me lavishly with food and drink on the occasions of my visits to Salamanca. To his scholarship and liberality I owe a great debt.

Dr. Chaplais guided my first steps in the science of Diplomatic and kindly read and commented upon early drafts of chapter 3. Professor the Reverend Colin Morris, of the University of Southampton, with great generosity read the whole [vi] of my thesis and made a number of suggestions which have been of the utmost value to me in my revision of the text. Mr. Bernard Barr, of York Minster Library, put at my disposal his extensive knowledge of medieval Latin, and scrutinized the curious and sometimes bizarre language of the documents printed in the appendix: I am grateful to him for the correction of errors and for some conjectural readings where the originals were damaged or illegible.

Fulford, York
April 1976