Following the example of his mother Queen Elizabeth II, the new monarch of the United Kingdom has officially chosen his first given name as regnal name: King Charles III. I previously speculated that the new king might choose the names George VII , Philip, or, as a longshot, King Arthur . Historically, it’s popular for monarchs to choose their first names–since the creation of the United Kingdom, the only monarchs to break the pattern by reigning with a subsequent given name have been Victoria, Edward VII, and George VI.
Regnal names in the United Kingdom have a complex history, particularly those which were used for monarchs of England or Scotland prior to the unification of the two kingdoms. Until 1603, England and Scotland had separate monarchies, although royals of the two kingdoms frequently intermarried. (All English monarchs since Henry II were descendants of Malcolm III of Scotland, and all Scottish monarchs since James II of Scotland were descendants of Edward III of England; see this chart.) Queen Elizabeth I’s closest heir after her death was her first cousin twice removed (in two ways), King James VI of Scotland, who subsequently became known as King James I of England.
Between 1603 and the creation of the Kingdom of Great Britain in 1707, monarchs of England and Scotland could have two different regnal names, depending upon the lineage of their chosen name in each kingdom. James’s successors Charles I and Charles II were not affected by this rule, as Charles was a new regnal name for both kingdoms. Charles II was succeeded by his brother James, who became known as James II in England and James VII in Scotland. After the Glorious Revolution in 1688, James’s daughter Mary and her husband (and first cousin) William were invited to rule as co-monarchs of England and Scotland. She became Mary II in both kingdoms, as the name had a single predecessor in each, while he became William III of England and William II of Scotland. William survived his wife and was succeeded by her sister Anne, another new regnal name in both places.
The two countries were unified in 1707, but regnal names would not be affected by the change for another century, as the next monarch was George I—another new regnal name—and was succeeded by three more Georges. King George IV was succeeded in 1830 by his younger brother William Henry, Duke of Clarence, whose regnal name William IV followed upon three earlier English monarchs.1 I have not read of any Scottish objection to this regnal name. William IV was succeeded by his niece Alexandrina Victoria of Kent and Strathearn, whose regnal name Victoria had not been previously used. Her son Albert Edward, Prince of Wales succeeded his mother as King Edward VII, following upon six earlier English monarchs. 2 This choice apparently caused some offense in Scotland, as there had been no earlier Scottish monarch of that name, “and on many ceremonial occasions Scottish authorities omitted the offensive numeral altogether .” Edward VII’s son reigned as George V, followed by the brief reign of Edward VIII, who was succeeded by his brother George VI, father of Elizabeth II.
The regnal name Elizabeth II again caused some offense in Scotland, including a 1953 lawsuit, MacCormick v Lord Advocate , on whether the Queen was entitled to use the numeral “II” in Scotland, as there had been no earlier monarch of that name in Scotland. The lawsuit was dismissed on the grounds that the numbering of monarchs was part of the royal prerogative, although Prime Minister Winston Churchill offered a solution on the occasional issue:
Although I am sure neither The Queen nor her advisers could seek to bind their successors in such a matter, I think it would be reasonable and logical to continue to adopt in future whichever numeral in the English or Scottish line were higher. Thus if, for instance, a King Robert or a King James came to the throne he might well be designated by the numeral appropriate to the Scottish succession, thereby emphasising that our Royal Family traces its descent through the English Royal line from William the Conqueror and beyond, and through the Scottish Royal line from Robert the Bruce and Malcolm Canmore and still further back. Her Majesty’s present advisers would for their part find no difficulty in accepting such a principle. From this it naturally follows that there should not in their view be any difficulty anywhere in acknowledging the Style and Title of Her present Majesty.
There has not yet been a reason to implement Churchill’s solution. The next heir after Charles III, William [Arthur Philip Louis], Prince of Wales, shares a first name with a higher number of past monarchs in England, but his subsequent names have not been used in either kingdom. The first name of William’s eldest child Prince George [Alexander Louis] of Wales has only been used since the union of Great Britain. If Prince George chose the regnal name Alexander, he could choose the name Alexander IV, after the three earlier Scottish monarchs. Considering the longevity of King Charles III’s parents, the question of the next regnal name will likely not be decided for a long time to come.
1 See here for an amusing story of whether the Duke of Clarence would be William IV or Henry IX.
2 There were also three earlier King Edwards during the Anglo-Saxon period before the Norman Conquest: Edward the Elder (reigned 899-924), Edward the Martyr (reigned 975-78), and Edward the Confessor (reigned 1042-66). However, the counting of later kings of England and the United Kingdom starts with Edward I “Longshanks” (reigned 1272-1307).