Democracy means government by discussion, but it is only effective if you can stop people talking. ~ English politician Clement Atlee
The roots of British parliamentary government trace to the 13th century Magna Carta, when King John was called to account by the nobility. The bicameral parliament that evolved in the following century served as a model for others throughout the world.
The lower house of Parliament – the House of Commons – is an elected body of 650, known as Members of Parliament (MPs). Members are elected to represent constituencies (districts) by first-past-the-post and hold their seats until Parliament is dissolved. 533 constituencies are in England, 59 in Scotland, 40 in Wales, and 18 in Northern Ireland.
The US holds its elections on Tuesdays. In the UK, Thursday is election day. This convention dates to 1931, when the electoral commission set the day to coincide with market day, to make it easier for those who had travel to town to cast their ballots.
Though there are several political parties in the UK, the centre-right Conservatives (aka Tories) and centre-left Labour are by far the major parties. Labour replaced the aptly named Liberal party as the Tories’ main rival in the late 1920s.
The upper house of Parliament – the House of Lords – comprises appointed landed nobility (Lords Temporal) and clergy (Lords Spiritual).
Lords Temporal are appointed by the monarch on advice of the Prime Minister or the House of Lords Appointments Commission. Some are hereditary peers: lordship passed down through the generations.
Lords Spiritual are appointed by the Church of England. They now number no more than 26 out of 819 in the House of Lords.
The size of the House of Lords has varied greatly through time. From ~50 in the early 1700s, Lords proliferated to 1,330 in 1999. Peers were pruned the next year to 669, but in the early 21st century the number of Lords again grew.
The power of the House of Lords has waxed and waned over the centuries. Nobility suffered during the civil wars of the 15th century (Wars of the Roses) but remained more powerful than the House of Commons until the mid-17th century, when Lords’ power evaporated in the wake of the English Civil War. The House of Lords regained stature during the 19th century but remains subordinate to the lower House of Commons.
The House of Lords holds the government to account, scrutinizing bills approved by the House of Commons. The House of Lords cannot veto bills, but may delay passage, and so force reconsideration.
Most bills are introduced in the Commons, but Lords may introduce legislation, though not money bills, which are beyond their purview.
In 2015, the House of Commons passed a measure to cut tax credits the next year. Objecting to a reduction of welfare for those most in need, the Lords rejected the bill, delaying its passage. This raised a constitutional question, as to whether the House of Lords had the right to interfere. In this instance, to stifle debate in the Commons, the bill was set as a statutory instrument, not a money bill, which the House of Lords could not have touched.
Theoretics aside, the British government is primarily held accountable by the House of Commons. The prime minister (PM) stays in office only as long has s/he retains MP majority support.
Since 2011, Commons terms are nominally 5 years. But a vote of no confidence in the prime minister brings about a general election. A prime minister may resign, in which case the premiership goes to whoever can command a majority in the House of Commons.