What was the origin of the British Monarchy?

They were originally warlords who ruled fairly small chunks of the British Isles by force. Eventually, in Saxon times, Edward of England managed to take over the whole of England. The Saxon Monarchy came to an end when William the Conqueror took over (by force again). All subsequent monarchs claim they are descended from him - although the line became a bit dubious when Henry VII took over (by force yet again). A few monarchs later, we ran out and had to borrow one from Scotland. After a civil war, the Commonwealth (a military dictatorship) and a couple of revolutions, parliament settled the crown on the descendants of the Electress Sophia of Hanover (a descendant of James VI of Scotland who became James I of England). Our present lot are descended from her.