In the 11th century the Danish King Canute united all the kingdoms of Great Britain, just in time for Duke William II of Normandy to conquer the land. The Normans used their well-practiced skills to assimilate into the local population and help develop the language and culture of Great Britain.
Henry VIII (1509-47) was the first king to turn his attention to the sea, resulting in Great Britain becoming a world power by the time of Elizabeth I (1558-1603).
By the 19th century, Great Britain -- now the United Kingdom -- had travelled the globe building one of the biggest empires ever seen. This lasted until the 20th century, when two world wars exhausted the UK's resources and set the stage for independence in the colonies.
United Kingdom on Wikipedia