Ernest Augustus was King of Hanover from 20 June 1837 until his death in 1851. As the fifth son of George III of the United Kingdom and Hanover, he initially seemed unlikely to become a monarch, but none of his elder brothers had a legitimate son. When his elder brother William IV, who ruled both kingdoms, died in 1837, his niece Victoria inherited the British throne under British succession law, while Ernest succeeded in Hanover under Salic law, which barred women from the succession, thus ending the personal union between Britain and Hanover that had begun in 1714.

William IV was King of the United Kingdom of Great Britain and Ireland and King of Hanover from 26 June 1830 until his death in 1837. The third son of George III, William succeeded his elder brother George IV, becoming the last king and penultimate monarch of Britain's House of Hanover.