Liber Landavensis, the Book of Llandaf (Aberystwyth, National Library of Wales MS 17110E), a Gospel Book cum History cum Cartulary, is at once the most difficult and the most exciting document of the twelfth-century Church known to the present writer. Whether one's interests turn towards hagiography, post-Roman land tenure, ecclesiastical politics, the development of the Welsh language, early medieval diplomatic, or simply forgery on a grand scale, Liber Landavensis (hereafter LL) is a rich but challenging source. It was justly described by Adrian Morey and C. N. L. Brooke as a ‘summit of achievement in the production of bogus documents’ in Britain, and therein lies its notoriety and much of its difficulty. Few works better illustrate their contention that in the twelfth century the worlds of the hagiographer, the charter forger, and the historian coincided closely in the service of the spiritual and temporal power and privileges of the churches for whom such men doctored or composed.

In LL the saints’ Lives, the twelfth-century documents, and the charters are inextricably inter-related, and a full understanding of it and its context will not come until the study of all three elements has been fully integrated. The first two of the three have been studied in detail by John Reuben Davies. His work supplements G. H. Doble's intelligent, but often incomplete, work on the Vitae, and J. Conway Davies's and C. N. L. Brooke's interpretations of LL in relation to its documents about the struggles of Bishop Urban of Llandaf in 1119–34 against the bishops of St Davids and Hereford, the Pope, and the ‘invasion of monks’ from houses such as Gloucester and Tewkesbury.

The third element in LL is the 159 charters which purport to date from the fifth or sixth centuries to the eleventh. The present book is intended to supplement the two substantial books which Wendy Davies devoted to their evaluation. Her two books, the result of a decade of study, were among the most important works on early Welsh history published in the twentieth century, and in turning attention back to the LL charters and their historical uses they performed a timely service. As she was aware, however, they were far from exhausting the potential of the charters. The Llandaff Charters was intended as ‘a useful guide to their understanding and a coherent framework within which others can approach them’ (p. vii).