A transcription of Royal Letters Patent from 1607 granting sovereignty of the Isle of Man, its castle, and regalities to Henry Earl of Northampton and Robert Earl of Salisbury. The grant was made at the petition of William Earl of Derby and other heirs of Ferdinando Earl of Derby. This document is a foundational record of early modern Manx lordship and demonstrates the mechanisms of royal grant and feudal tenure that preceded the 1765 Revestment.