Estimates of inbreeding are rather scarce for British populations. A number of studies, especially of Scottish island populations, have focused on pedigree analysis, whilst others have used survey methods or inference from isonymy. By comparison with continental Europe, however, little is known of the historical development of inbreeding. This is undoubtedly due to the lack of evidence from dispensations to marry blood relatives, which are routinely available in the records of marriage of the Roman Catholic church. The paper uses as its data source the Faculty Office Registers, 1534-1540, which were the product of a new system of issuing dispensations following the Dispensations Act of 1533, and which are among the earliest administrative records of the Church of England, founded as a result of Henry VIII's breach with Rome. Dispensations are recorded in the Faculty Office until 1540, when all prohibitions on marriage beyond the proscribed relationships laid down in Leviticus were lifted. The data suggest surprisingly low levels of consanguineous marriage, including a lack of first-cousin marriages. These findings are discussed in terms of the reliability of the archive, and of the social and religious views attending marriage between blood relatives in the medieval and early modern periods.