After Edward I conquered Wales in 1283, the country was divided into two different areas. The land that the king controlled became known as the Principality. This area was ruled in a similar way to England. The Principality was divided into shires (counties) which were governed by officials appointed by the king. About two-thirds of Wales continued to be ruled by Marcher Lords. These lands had been conquered by the Normans in the 11th and 12th centuries.

At the Battle of Bosworth in 1485, Henry Tudor won the English throne from Richard III. Henry was a Welsh man who had relied heavily on Welsh soldiers to help him win victory. After he became king. Henry VII rewarded many Welsh leaders who had helped him with titles and government posts.

When Henry VIII was king he became concerned with the way that Marcher Lords ruled their lands. Reports he received suggested that the Marcher Lords were failing to maintain law and order. It was argued that criminals were breaking the law in England and then escaping to Wales. One report claimed that a Welsh official was receiving payment from twenty-three murderers and twenty-five thieves in return for protecting them from English justice.

Henry's fears about the power of the Marcher Lords grew after his break with the Catholic church in 1534. Some of these Marcher Lords were supporters of the Pope and Henry was worried that they might rebel against him. Henry was also warned that Catholic monarchs in France and Spain might try to invade England by landing their soldiers on the poorly defended coasts of Wales. To protect himself against this possibility. Henry decided to take control of the whole of Wales.

Between 1536 and 1543, the English Parliament passed a series of laws that became known as the Acts of Union. The Principality and the land controlled by the Marcher Lords were now joined together to form a united Wales.

Like England, the whole of Wales was now divided into shires. The administration of these shires was based on the shires in England with each one having its own Justice of the Peace.

Under the terms of the Act of Union, Wales was granted permission to be represented in Parliament. In 1542, twenty seven people in Wales were elected to sit in the House of Commons. Most of these elections were not contested and the person sent to the House of Commons was usually selected by a few wealthy families in the area.

One aspect of the Act of Union upset a large number of people in Wales. The act stated that all people that were chosen to represent Wales as officials or Members of Parliament had to be able to speak English. It also stated that the law-courts in Wales had to use the English language.