This is an examination of how and why medieval kings declared certain properties immune from their own power. The author argues that they were not compelled by weakness, but rather by a need to show strength and reaffirm status and exercise authority, and that we need a new understanding of the political and social exchanges of the period. The declaration of immunities were really instruments used by kings and bishops to forge alliances with the noble families and monastic centres which were the essence of their authority.