George IV (George Augustus Frederick) was king of the United Kingdom of Great Britain and Ireland and Hanover from 29 January 1820 until his death on 26 June 1830. He had earlier served as The Prince Regent when his father, George III, suffered from a relapse into insanity from an illness that is now suspected to have been porphyria. The Regency, George's nine-year tenure as Prince Regent, which commenced in 1811 and ended with George III's death in 1820, was marked by victory in the Napoleonic Wars in Europe.

George was a stubborn monarch, often interfering in politics, especially in the matter of Catholic emancipation, though not as much as his father. For most of George's regency and reign, Lord Liverpool controlled the government as Prime Minister.

William IV (William Henry) was King of Hanover and of the United Kingdom of Great Britain and Ireland from 26 June 1830 until his death on 20 June 1837. William, the third son of George III and younger brother and successor to George IV, was the last king and penultimate monarch of the House of Hanover.

He served in the Royal Navy in his youth and was, both during his reign and afterwards, nicknamed the Sailor King. He served in North America and the Caribbean, but saw little actual fighting. Since his two older brothers died without leaving surviving legitimate issue, he inherited the throne when he was sixty-four years old. His reign saw several reforms: the poor law was updated, child labour restricted and slavery abolished throughout the British Empire. One of the most important pieces of legislation was the Reform Act 1832, which refashioned the British electoral system. Though William did not engage in politics as much as his brother or his father, he was the last monarch to appoint a Prime Minister contrary to the will of Parliament. During his reign, his other kingdom, Hanover, was granted a short-lived liberal constitution.

Though Victoria ascended the throne at a time when the United Kingdom was already an established constitutional monarchy in which the king or queen held few political powers, she still served as a very important symbolic figure of her time. The Victorian era represented the height of the Industrial Revolution, a period of significant social, economic, and technological progress in the United Kingdom. Victoria's reign was marked by a great expansion of the British Empire; during this period it reached its zenith, becoming the foremost global power of the time.

From the age of 12 George served in the Royal Navy, but upon the unexpected death of his elder brother, Prince Albert Victor, Duke of Clarence and Avondale, he became heir to the throne and married his brother's fiancée, Mary of Teck (known as "May" to her family after her birth month). Although they occasionally toured the British Empire, George preferred to stay at home with his stamp collection and lived what later biographers would consider a dull life because of its conventionality.

When George's father, King Edward VII died in 1910, he became King-Emperor. He was the only Emperor of India to be present at his own Delhi Durbar, where he appeared before his Indian subjects crowned with the Imperial Crown of India, created specially for the occasion. During World War I he relinquished all German titles and styles on behalf of his relatives who were British subjects; and changed the name of the royal house from Saxe-Coburg and Gotha to Windsor. During his reign, the Statute of Westminster separated the crown so that George ruled the dominions as separate kingdoms, preparing the way for the future development of the Commonwealth. His reign also witnessed the rise of socialism, fascism, Irish republicanism and the first Labour ministry, all of which radically changed the political spectrum.

Before his accession to the throne, Edward VIII held the titles of Prince Edward of York, Prince Edward of Cornwall and York, Duke of Cornwall, Duke of Rothesay, and Prince of Wales (all with the style Royal Highness). As a young man, he served in World War I, undertook several foreign tours on behalf of his father, and was associated with a succession of older, married women.

Only months into his reign, Edward caused a constitutional crisis by proposing marriage to the American divorcée Wallis Simpson. Although legally Edward could have married Mrs. Simpson and remained king, the prime ministers of his various realms opposed the marriage, arguing that the people would never accept her as queen. Edward knew that the ministry of British Prime Minister Stanley Baldwin would resign if the marriage went ahead; this could have dragged the King into a general election, thus ruining irreparably his status as a politically neutral constitutional monarch. Rather than give up Mrs Simpson, Edward chose to abdicate, making him the only monarch of Britain, and indeed any Commonwealth realm, to have voluntarily relinquished the throne. With a reign of 325 days, he is one of the shortest-reigning monarchs in the history of any of his countries, and was never crowned.

As the second son of King George V, he was not expected to inherit the throne and spent his early life in the shadow of his elder brother, Edward. He served in the Royal Navy during World War I, and after the war took on the usual round of public engagements. He married Lady Elizabeth Bowes-Lyon in 1923, and they had two daughters, Elizabeth (who succeeded him as Queen Elizabeth II) and Margaret.

At the death of his father in 1936, the future George VI's brother ascended the throne as Edward VIII. However, less than a year later Edward expressed his desire to marry the twice-divorced American socialite Wallis Simpson. For political and religious reasons, the British Prime Minister, Stanley Baldwin, advised Edward that he could not marry Mrs Simpson and remain king. So, Edward abdicated in order to marry. By reason of this abdication, unique in the history of the British Isles (previous abdications were forced by military or political pressures), George VI ascended the throne as the third monarch of the House of Windsor.

In addition to the United Kingdom, Elizabeth II is also Queen of Canada, Australia, New Zealand, Jamaica, Barbados, the Bahamas, Grenada, Papua New Guinea, the Solomon Islands, Tuvalu, Saint Lucia, Saint Vincent and the Grenadines, Belize, Antigua and Barbuda, and Saint Kitts and Nevis, in each of which she is represented by a Governor-General. The 16 countries of which she is Queen are known as Commonwealth realms, and their combined population, including dependencies, is over 129 million. In theory her powers are vast; in practice (and in accordance with convention) she herself rarely intervenes in political matters. In the United Kingdom at least, however, she is known to take an active behind-the-scenes interest in the affairs of state, meeting regularly to establish a working relationship with her government ministers.

Elizabeth II holds a variety of other positions, among them Head of the Commonwealth, Supreme Govenor of the Church of england, Duke of Normandy, Lord of Mann, and Paramount Chief of Fiji. Her long reign has seen sweeping changes in her realms and the world at large, perhaps most notably the dissolution of the British Empire (a process that began in the last years of her father's reign) and the consequent evolution of the modern Commonwealthy of Nations.