By the Late Middle Ages, Great Britain was separated into the Kingdoms of England and Scotland. Power in Ireland fluxed between Gaelic kingdoms, Hiberno-Norman lords and the English-dominated Lordship of Ireland. A similar situation existed in the Principality of Wales, which was slowly being annexed into the Kingdom of England by a series of laws. During the course of the 15th century, the Crown of England would assert a claim to the Crown of France, thereby also releasing the King of England as from being vassal of the King of France. In 1534, King Henry VIII, at first having been a strong defender of Roman Catholicism in the face of the Reformation, separated from the Roman Church after failing to secure a divorce from the Pope. His response was to place the King of England as "the only Supreme Head in Earth of the Church of England", thereby removing the authority of the Pope from the affairs of the English Church. Ireland, which had been held by the King of England as Lord of Ireland, but which strictly speaking had been a feudal possession of the Pope since the Norman invasion was declared a separate kingdom in personal union with England.

During the end of the Middle Ages which two kingdoms was Great Britain divided into?