The 1801 Act of Union merged the Kingdom of Ireland and the Kingdom of Great Britain (itself a merger of England and Scotland in 1707 under the 1707 Act of Union) to create the United Kingdom of Great Britain and Ireland.
Under the terms of the merger, Ireland continued to have over 100 MPs representing it in the united parliament, meeting in the Palace of Westminster. Part of the trade-off was to be the granting of Catholic Emancipation. However this was blocked by King George III who argued that emancipating Roman Catholics would breach his Coronation Oath.
The flag created by the merger of the Kingdoms of Great Britain and Ireland in 1801 still remains the flag of the current United Kingdom. Known as the Union Flag or the Union Jack, it combines the flags of England and Scotland with St. Patrick's flag from Ireland. The upright red cross, St. George's Cross, represents England. The Blue background, on which St. Andrew's Saltire (in the shape of a white 'x') appears, represents Scotland, while the diagonal red 'x' which overlays the white x' on the blue background of Scotland, is known as 'St. Patrick's Cross' and represents Ireland. See also: