Before coming to the substance of this paper, I feel that I must define its purpose somewhat more closely than I have done in the title which I have given to it. A study of the state and landed interests, of course, could embrace most of the domestic and much of the external histories of France and England in the thirteenth century, I shall be concerned with much less than that—with a problem which nevertheless seems to me to be of the first importance in any study of the social and economic policies (if that phrase be not too anachronistic) of medieval governments. I mean the break-up and alienation of feudal tenements in the thirteenth century, some of the causes and consequences thereof, and some of the attempts made to deal with the difficulties thereby occasioned. This still remains a large subject, and at best this paper is an attempt at synthesis, even of vulgarisation, which rests, in the main, upon the work of others. In particular, I have drawn heavily upon Professor Plucknett's study of the legislation of Edward I, and I was encouraged to venture upon some comparisons with France because he has also shown, I feel, that such comparisons may not be without value.