The Dukes of Brunswick-Lüneburg became the Electors of Hanover (Hannover is the German spelling) in 1692.
Electors of Hanover, 1692-1814
In 1803, Hanover was occupied by France, and did not return to the control of its Elector until 1814. In the meanwhile, however, Hanoverian ministers continued to operate out of London, and maintained their own separate diplomatic service (which maintained links to countries like Austria and Prussia, with whom the United Kingdom itself was technically at war). In 1814, Hanover became a Kingdom.
Kings of Hanover, 1814-1866
The thrones of the United Kingdom and Hanover diverged in 1837 as Hanover, unlike the U.K., was under the Salic law, and so did not pass to Queen Victoria. Her uncle, the Duke of Cumberland, succeeded as
Hanover was annexed by Prussia in 1866 as a result of Hanover's participation on Austria's side in the Austro-Prussian (or Seven Weeks') War.
Heads of the Royal House of Hanover since 1866
See also: House of Hanover