In The Agrarian Problem in the Sixteenth Century, R. H. Tawney described a wide range of possible constraints that customary tenure might impose upon lords and tenants. He noted that customary rents were normally fixed, and that during a period of rising land values lords could seek to increase their share of income from the land in a limited number of ways. They might overturn custom and persuade the tenantry to convert to leasehold, or retrieve the situation through increased fines ‘so as to get in a lump sum what he could not get by yearly instalments’. This last statement suggests that it was possible to increase fines to keep pace with the rise in market rents and that such increases could allow transfers from tenant to lord which would equate to the ‘lost’ rents. This chapter uses a detailed study of a tenant right estate in north-west England to demonstrate a number of points which have a more general application for other forms of customary tenure. It examines two aspects of the power struggle between lords and customary tenants on the Hornby Castle estates in north Lancashire. First, it identifies the potential income from the customary lands and quantifies the relative shares accruing to lord and tenants. This demonstrates how substantial the benefits were for manorial tenants who defeated their lords' attempts to raise rents and fines, and retained their tenures on customary terms.