History of the formation of the United Kingdom Kingdom of England (which included Wales and controlled Ireland) and the Kingdom of Scotland. The once independent Principality of Wales fell under the control of English monarchs from the Statute of Rhuddlan in 1284. The Union of Crowns in 1603, the accidental consequence of a royal marriage one hundred years earlier, united the kingdoms in a personal union, though full political union in the form of the Kingdom of Great Britain required a Treaty of Union in 1706 and Acts of Union in 1707 (to ratify the Treaty). The Act of Union 1800 united the Kingdom of Great Britain with
Acts of Union 1800 Acts of Union 1800 The Acts of Union 1800 (sometimes erroneously referred to as a single Act of Union 1801) were parallel acts of the Parliament of Great Britain and the Parliament of Ireland which united the Kingdom of Great Britain and the Kingdom of Ireland (previously in personal union) to create the United Kingdom of Great Britain and Ireland. The acts came into force on 1 January 1801, and the merged Parliament of the United Kingdom had its first meeting on 22 January 1801. Both acts remain in force, with amendments, in the United Kingdom of Great Britain and