George IV (1762-1830), King of the United Kingdom and Lord of Mann from 1820 to 1830, in whose reign the Atholl claims were finally bought out.

He inherited an arrangement rather than made one. The land revenues and other possessions acquired in the Island had been placed under the management of the department of Woods and Forests and treated as part of the hereditary revenues of the Crown. George IV, following his father's example, placed those revenues at the disposal of the House of Commons for his life, and the House then made other provision for the Crown, as his successors did after him.

The last of the Atholl business was settled while he reigned. By 1826 a correspondent of the Home Office could report that the treaty between the Crown and the Duke was rapidly advancing, that the Duke's own acquired property was not involved in it, Castle Mona included, and could ask whether Castle Mona might be applied to some public purpose, since Government House would soon have to become the gaoler's.