The first king of all of England was Athelstan (895-939 AD) of the House of Wessex, grandson of Alfred the Great and 30th great-grand uncle to Queen Elizabeth II. The Anglo-Saxon king defeated the last of the Viking invaders and consolidated Britain, ruling from 925-939 AD.

Starting with the reign of William the Conqueror, the monarchy was passed from the king to his firstborn son. This was changed in 1702 when British Parliament passed the Act of Settlement, which stated that upon King William III’s death, the title or monarch would pass to Anne and the “heirs of her body,” meaning a woman could inherit the throne—as long as there wasn’t a male heir available to take her place. At the time, English common law held that male heirs inherited the throne before their sisters. In a nod to the power of the Church of England, the Act of Settlement also stated that any heir who married a Roman Catholic would be removed from the line of succession.

The rules around who could inherit the British throne were not updated again until 2013, when Parliament passed the Succession to the Crown Act. It shifted the line of succession to an absolute primogeniture system, meaning the kingdom would pass to the first-born heir, regardless of their gender.

The Royal Marriage Act of 1772 granted the monarch the right to veto any match within the royal family. It was passed in response to George III’s anger over his younger brother Prince Henry’s marriage to the commoner Anne Horton.

Ever since, royals hoping to wed have had to ask the Crown’s permission to marry. This permission was not always granted. Queen Elizabeth II famously refused her sister Princess Margaret’s request to marry Peter Townsend, a war hero the queen considered unsuitable because he also happened to be a commoner and a divorcé.

This power was curtailed slightly with the passage of the Succession to the Crown Act of 2013, which enabled heirs outside of the first six in the line of royal succession to marry without the monarch’s permission.

Until the early 20th century, reigning sovereigns were referred to by their family or “house” names. For example, Henry VIII and his children were all Tudors, followed by a series of Stuarts.

This changed during World War I, when England was at war with Germany. King George V had some awkward family connections: His grandfather, Prince Albert, was born in Germany, and through him George V inherited the title of head of the House of Saxe-Coburg-Gotha. To create a sense of distance between the British throne and their overseas relations, the family name was replaced with a more modern, English surname: Windsor. The name was inspired by Windsor Castle, which was founded by William the Conqueror.

British royals were marrying commoners as early as the 15th century, though in a family where bloodlines determine power, the pairings were always controversial. In 1464, King Edward IV secretly married commoner Elizabeth Woodville, a widow. The future King James II also married a commoner: Anne Hyde, whom he’d gotten pregnant (she passed away before he became king).

With the passage of the Royal Marriages Act of 1772 in response to Prince Henry’s marriage to the commoner Anne Horton, royal-commoner marriages virtually disappeared for almost 250 years.

As societal rules around marriage, divorce, and partnership shifted, so did royal marriages. Both children of Prince Charles and Princess Diana were permitted to marry commoners: Prince William married Kate Middleton, the daughter of parents who own a party supplies company, in 2011. His brother, Harry, married American actress Meghan Markle in 2018.

Getting a royal divorce was a royal pain until very recently; it was only in 2002 that the Church of England allowed divorced people to remarry. Given that the monarch is also the head of the Anglican Church, heirs to the throne were effectively forbidden from marrying divorced people—or getting divorced themselves. (Ironic, since it was King Henry VIII who founded the church after the Catholic Church wouldn’t grant him an annulment from his first wife, Catherine of Aragon.)

Since the Royal Marriage Act of 1772 granted the monarch veto power over marriages in the royal family, for centuries, the stigma around divorce meant any proposed union between royalty and a divorced person was a non-starter.

In 1820, King George IV went before a parliamentary panel in an attempt to divorce his wife, Caroline of Brunswick, whom he accused of being unfaithful. He succeeded only in raising a scandal—and reinforcing the message that you can’t hold a crown and divorce papers at once.

In 1936, Edward VIII abdicated the throne in order to marry the twice-divorced American Wallis Simpson. He was the last royal forced to choose between love and succession. Before the 2002 Church ruling, Queen Elizabeth II’s sister, Princess Margaret, was permitted to divorce in 1978. And in 1996, Elizabeth II approved the divorce between her son Prince Charles and Princess Diana. Charles would go on to marry the also-divorced Camilla Parker Bowles in 2005, while his son, Harry, would marry divorcée Meghan Markle in 2018.

In addition to being Head of the Anglican Church, the British monarch is also Head of the Commonwealth, an association of 54 independent countries, most of which were once colonies or outposts of the British Empire.

Elizabeth II was queen of 16 countries that are part of the Commonwealth: Antigua and Barbuda, Australia, The Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, the Solomon Islands, Tuvalu, and the United Kingdom.