History of the monarchy of the United Kingdom
The history of the monarchy of the United Kingdom and its evolution into a constitutional and ceremonial monarchy is a major theme in the historical development of the British constitution. The British monarchy traces its origins to the petty kingdoms of Anglo-Saxon England and early medieval Scotland, which consolidated into the kingdoms of England and Scotland by the 10th century.
Source: Wikipedia — History of the monarchy of the United Kingdom (CC BY-SA 4.0)