Short answers, pulled from the story.
The United Kingdom of Great Britain and Ireland was established on the 1st of January 1801 by the Acts of Union, which merged the Kingdom of Great Britain and the Kingdom of Ireland into one state. The union was driven by British fear that an independent Ireland might side with Revolutionary France during the ongoing war, following the Irish Rebellion of 1798.
The Great Irish Famine was caused by the failure of the potato crop in the 1840s. The British government did little to help the starving poor, and over one million people died while another million emigrated within a few years, mostly to Britain and the United States. The government's inaction is remembered in Ireland to this day as oppression by the British Empire.
The Peterloo Massacre occurred on the 16th of August 1819 in Manchester, when a local militia charged into an orderly crowd of sixty thousand people who had gathered to demand parliamentary reform. Eleven people died and hundreds were injured. The government responded by passing the Six Acts, which outlawed public meetings of more than fifty people.
The Reform Act 1832 sharply reduced the number of rotten and pocket boroughs controlled by powerful families, redistributed parliamentary seats by population, and added two hundred and seventeen thousand voters to an electorate of four hundred and thirty-five thousand in England and Wales. It weakened the power of the landed gentry and gave the professional and business middle class a significant voice in Parliament for the first time.
The Irish War of Independence resulted in British recognition of the Irish Free State in 1922. Six northeastern counties of Ireland opted out of joining the Free State and remained part of the Union. On the 12th of April 1927, the Royal and Parliamentary Titles Act formally renamed the state the United Kingdom of Great Britain and Northern Ireland.
The United Kingdom suffered almost three million casualties in the First World War, a generation known as the "lost generation." The government's share of GDP rose from eight percent in 1913 to thirty-eight percent in 1918, and Britain was forced to use up its financial reserves and borrow large sums from the United States to sustain the war effort.