Since the Norman conquest of England in the 11th century, it was presumed that kings would simply pass the power to rule to their first-born son. This line of succession, known as primogeniture, was also used to determine non-royal heirs to property and wealth.

However, almost from the very beginning, succession to the throne, first in England and now in the United Kingdom (which includes England, Scotland, Wales and Northern Ireland), was rarely so straightforward.

Indeed, factors such as war, political turmoil and the inability of some monarchs to produce a suitable male heir have resulted in confusion and tumultuous transfers in power.

And now, under the United Kingdom’s current constitutional monarchy form of government, the protocol for succession to the throne is more complicated still—and is overseen by Parliament, the legislative branch of the national government.

Beginning with the first Norman King of England, William I or William the Conqueror, the title of ruling monarch was passed from the king to his first-born son, usually at the time of the former’s death.

Despite the fact that this straightforward transition didn’t always come to pass—for a variety of reasons—the process remained in place, although not as a written law per se, for some seven hundred years.

As England evolved into a democratic form of government—specifically a constitutional monarchy—in the late 1600s, the country’s leaders decided to codify the succession of power.

The result was a law known as the Act of Settlement of 1701. This landmark legislation established that, at the time of King William III’s death, the title of ruling monarch would be passed on to queen-in-waiting Anne and the “heirs of her body.” English common law at the time defined heirs essentially by male-preference primogeniture, meaning that male heirs would have the first right to the throne over their sisters.

And, with the Church of England well established as the country’s national church, the law also prohibited Roman Catholics from inheriting the throne. Heirs who chose to marry Roman Catholics were also removed from the line of succession.

Despite its obvious discrimination against female heirs to the throne as well as adherents to the Roman Catholic religion, the Act of Settlement of 1701 officially remained the law of the land in the United Kingdom until 2013, with Parliament’s passage of the Succession to the Crown Act.

Seeking to eliminate the inherent discrimination of the original law, and working in consultation with Queen Elizabeth II and her heirs, Parliamentary representatives of the four nations that make up the United Kingdom agreed to modify the line of succession laws to change the male-preference primogeniture system to an absolute primogeniture system (first-born heir, regardless of gender).

The Succession to the Crown Act of 2013 also established that an heir could still inherit the throne even if they married a Roman Catholic and no longer required heirs outside of the first six in the line of succession to seek the ruling monarch’s permission to marry.

The new law officially took effect in 2015. However, the ban against heirs who are Roman Catholic from inheriting the throne remains in place, at least officially.

Similar modifications to the laws regarding line of succession in other constitutional monarchies around the world were made much earlier.

Belgium, for example, has used absolute primogeniture since 1991, and the system has been in place in the Kingdom of the Netherlands and in Sweden for decades. Spain, however, still uses a system of male-preference primogeniture.

Upon Queen Elizabeth II’s death on September 8, 2022, her eldest son Charles, the Prince of Wales, became King Charles III. Next in line to the throne is Charles' eldest son, Prince William, Prince of Wales, Duke of Cornwall and Cambridge. After William, the throne will pass to Prince George of Cornwall and Wales, his son with wife Catherine, Princess of Wales (née Kate Middleton). William and Kate’s other children, Charlotte and Louis, are next in line. William’s brother, Harry, Duke of Sussex, husband of Meghan Markle, is next in line, and their son, Archie Harrison Mountbatten-Windsor, is sixth in line to the throne.

Following Archie, the crown goes to his sister, Lilibet Mountbatten-Windsor, followed by the Duke of York, Prince Andrew, the third child of Queen Elizabeth II. Next is Princess Beatrice of York, Prince Andrew’s daughter and Queen Elizabeth II’s granddaughter, followed by Beatrice's daughter, Sienna Mapelli Mozzi. Next in line is Beatrice's sister, Princess Eugenie of York, followed by her son August Brooksbank.

Prince Edward, Earl of Wessex, is the youngest of Queen Elizabeth’s four children and thirteenth in line for the throne. His son, James, Viscount Severn, is fourteenth, and his daughter, The Lady Louise Mountbatten-Windsor, fifteenth.

Anne, The Princess Royal, the only daughter of Queen Elizabeth II, is sixteenth in line to the throne. Her son, Mr. Peter Phillips, is seventeenth, followed by his daughters, Miss Savannah Phillips and Miss Isla Phillips.

Queen Elizabeth’s granddaughter and the daughter or Princess Anne and Captain Mark Phillips, Zara Tindall, is 20th in line to the throne.

Succession. The Home of the Royal Family. Succession to the Crown Act 2013. Legislation.Gov.UK. Monarch vs. president: What’s the better succession system? National Constitution Center. Succession to the throne. Royal House of the Netherlands.