Great Britain and the United Kingdom

Over the centuries, Great Britain has evolved politically from several independent countries (England, Scotland, and Wales) through two kingdoms with a shared monarch (England and Scotland) with the union of the Crowns in 1603, a single all-island Kingdom of Great Britain from 1707, to the situation following 1801 in which Great Britain together with the island of Ireland constituted the larger United Kingdom of Great Britain and Ireland (UK).
The UK became the United Kingdom of Great Britain and Northern Ireland in the 1920s (1922) following the independence of five-sixths of Ireland as first the Irish Free State, a Dominion of the then British Commonwealth, and then later as an independent republic outside the British Commonwealth as the Republic of Ireland.

Union with Wales 1284
Wales became incorporated into England under the Statute of Rhuddlan in 1284, after it had been annexed by Edward I of England in 1282. Edward dubbed his eldest son Edward Prince of Wales, since which time the eldest son of each English monarch has borne the same title. In the Laws in Wales Acts 1535–1542, Wales became legally part of the Kingdom of England

Union of the Crowns of of England and Scotland 1603
The Crowns of England and Scotland were united in 1603 when James VI of King Scotland became James 1st King of England. In October 1604, one year later , he decreed that the Royal Title would use the term Great Brittaine to refer to the "one Imperiall Crowne" made up of England and Scotland.

Union with Scotland 1707
In 1707 The Acts of Union uniting England and Scotland under one Parliament and Crown came into effect. Queen Anne had recommended the union of the two kingdoms in her first speech to parliament in 1702..
In 1681 Anne had spent 10 months in Scotland (a stay not repeated by another British monarch until George IV).
On January 16th 1707 the Scottish Parliament passed an Act of Union, and on February 28th the Commons in England followed suit. Queen Anne gave the royal assent on March 6. This would bring into effect the Treaty of Union with its 25 Articles, the first of which declared:
"That the Two Kingdoms of Scotland and England, shall upon the 1st May next ensuing the date hereof, and forever after, be United into One Kingdom by the Name of Great Britain”.
It would dissolve both parliaments and establish a single Parliament for Great Britain, taking in 16 peers and 45elected members from Scotland and 190 peers and 513 members from England. Queen Anne attended a service of thanksgiving at St Paul’s Cathedral in London, wearing both the Order of the Garter and the Order of the Thistle.
Monetary union and a customs union were created. Scotland was allowed to have its own established (Presbyterian) church and England its established (Episcopal) church. Scottish law would remain in force and the Court of Session would decide it. Provisions of the Act of Settlement, 1701, were confirmed, so “that all Papists and persons marrying Papists, shall be excluded” from the throne.
A new Union flag combined the Cross of St Andrew (white diagonals on a blue ground) and the Cross of St George (a red cross).

Union with Ireland 1801
In 1800 the Act of Union with Ireland was passed by both the Irish and British parliaments despite much opposition. It was signed by George III in August 1800 to become effective on 1 January 1801.
Prime Minister Pitt intended to follow the Act of Union with other, more far reaching reforms, including Catholic Emancipation, but was thwarted by George III, who refused to break his Coronation Oath to uphold the Anglican Church.
The 1801 Act of Irish Union said that
* Ireland was to be joined to Great Britain into a single kingdom, the United Kingdom of Great Britain and Ireland.
* the Dublin parliament was abolished. Ireland was to be represented at Westminster by 100 MPs, 4 Lords Spiritual and 28 Lords Temporal (all were Anglicans).
* the Anglican Church was to be recognised as the official Church of Ireland.
* there was to be free trade between Ireland and Britain.
* Ireland was to keep a separate Exchequer and was to be responsible for two-seventeenths of the general expense of the United Kingdom.
* Ireland kept its own Courts of Justice and civil service.
* no Catholics were to be allowed to hold public office.
* there was to be no Catholic Emancipation.
The new kingdom was from then onwards unambiguously called the United Kingdom of Great Britain and Ireland.
In 1922, 26 of Ireland's 32 counties were given independence to form a separate Irish Free State - now the Republic of Ireland. The remaining truncated kingdom has therefore since then been known as the United Kingdom of Great Britain and Northern Ireland.