On the corresponding occasion last year, I ventured to offer some remarks on the subject of medieval Welsh lawbooks, and more particularly on the editing of them. When edited, they serve as historical evidence. I therefore propose on this present occasion to consider the sort of historical evidence that they contain, and the kind of historical question that they raise. As I have to operate within the narrow compass of an hour, I must limit my field of view, and this can be done quite simply. A Welsh lawbook was made up of a series of what, in the absence of a recognized technical term, may conveniently be called ‘tractates’. I am going to consider just one of those tractates. It is, in more than one sense, the most easily distinguishable of them all. It is also the one that forms the very first part of the text of the Welsh lawbooks, coming immediately after the opening prologue. From its situation at the very beginning of the text, it should be the most inescapable document in the lawbooks—though, as Edgar Allan Poe demonstrated in a famous story, a document situated in the most obtrusive position is precisely the one that may most easily escape notice. It is quite a sizeable document, running to some twenty pages of modern print. It is extant both in medieval Latin and in medieval Welsh.