This is Chapter 1 of a comprehensive historical work analysing constitutional and administrative changes in the Isle of Man following the 1765 Revestment (transfer of sovereignty from the Duke of Atholl to the British Crown). It traces the evolution of the governor's role, the Tynwald Court's powers, judicial reforms, and the gradual expansion of Manx political autonomy from 1765 to approximately 1890. The chapter provides detailed examination of the 1866 constitutional reforms and financial negotiations between Westminster and the Manx Legislature.