Documents purporting to be those of Anglo-Norman lay men and women have survived in quite substantial numbers from before 1100. For lay estates they are often the only source that can be used alongside Domesday Book, and for the religious institutions which are the beneficiaries they are often the foundation charter or the earliest record of endowment. But interpreting them poses serious problems. They are often suspected of being forgeries. The eleventh century was a period of very decentralised document production everywhere in northern Europe: ‘each establishment created its own tradition’, leading inevitably to a great variety of diplomatic practice. This is even more obviously the case when dealing with non-royal productions, and makes criticism exceptionally difficult. Especially to historians approaching these documents backwards, coming to them with eyes used to the much more numerous baronial charters of the later twelfth and thirteenth centuries, many purported eleventh-century documents look distinctly eccentric, and all the worse for being studded with unnerving anticipations of later common forms. To use such significant source material with confidence there has to be some degree of consensus on authenticity. The more recent historiography of the subject has been about the mentality of the writer or forger, the ways in which documents can develop and their connection with more obviously narrative texts. The authors of eleventh-century charters are now likely to be seen as tentative amateurs unused to drafting such documents, but feeling their way towards the later common forms. This may be true, but it does nothing to solve the problem of authenticity. Discussions of group memory, literacy and the status of written testimony presuppose knowledge of which texts, or which parts of which texts, were written in the eleventh century and which in the twelfth or later. Authenticity is an underlying issue in this work, but it is rarely tackled head on.

These documents can be subjected to various types of criticism, to do with the historical context in which they claim to have been drawn up – questions of the tenure of land and the dates of individuals named in them, for example. They can be examined one by one for the credibility of their content.