The formation of the United Kingdom of Great Britain and Northern Ireland has involved personal and political union across Great Britain and the wider British Isles. The United Kingdom is the most recent of a number of sovereign states that have been established in Great Britain at different periods in history, in different combinations and under a variety of polities. Historian Norman Davies has counted sixteen different states over the past 2,000 years.
By the start of the 16th century, the number of states in Great Britain had been reduced to two: the Kingdom of England (which included Wales and controlled Ireland) and the Kingdom of Scotland.