This is a comprehensive survey of medieval English mortmain legislation from both the point of view of the crown and that of the Church. It examines methods of enforcement and evaluates their success. It traces the emergence of licensing policies and the increasing exploitation of licences for fiscal purposes, while at the same time establishing that this was not their original purpose. The extent to which the Church was acquiring land on a threatening scale by the later thirteenth century is questioned, and the effects of the legislation on subsequent acquisition are assessed against the background of new fashions in ecclesiastical patronage and a more hostile economic climate. The statutes of 1279 and 1391 are well known. What this study shows is how much variation lay behind the apparently straightforward system of licensing and how closely the issue of mortmain tenure was related to wider social, political and economic considerations.