### Instruction:
Without quoting directly from the text, briefly describe how the United Kingdom was formed from its constituent countries.

### Input:
The British monarchy traces its origins from the petty kingdoms of Anglo-Saxon England and early medieval Scotland, which consolidated into the kingdoms of England and Scotland by the 10th century. England was conquered by the Normans in 1066, after which Wales also gradually came under the control of Anglo-Normans. The process was completed in the 13th century when the Principality of Wales became a client state of the English kingdom. Meanwhile, Magna Carta began the process of reducing the English monarch's political powers. In the 16th century, English and Scottish monarchs played a central role in what became the religious English Reformation and Scottish Reformation. From 1603, the English and Scottish kingdoms were ruled by a single sovereign. From 1649 to 1660, the tradition of monarchy was broken by the republican Commonwealth of England, which followed the Wars of the Three Kingdoms. Following the installation of William III and Mary II as co-monarchs in the Glorious Revolution, the Bill of Rights 1689, and its Scottish counterpart the Claim of Right Act 1689, further curtailed the power of the monarchy and excluded Roman Catholics from succession to the throne. In 1707, the kingdoms of England and Scotland were merged to create the Kingdom of Great Britain, and in 1801, the Kingdom of Ireland joined to create the United Kingdom of Great Britain and Ireland. The British monarch was the nominal head of the vast British Empire, which covered a quarter of the world's land area at its greatest extent in 1921.

### Response:
The United Kingdom is now made up of England, Wales, Scotland and Northern Ireland. These countries were finally united in 1801, after England and Scotland (which had merged in 1707) were joined by the Kingdom of Ireland.