What if girls had always had an equal shot at the throne?
When the future King Edward VII found out as a seven-year-old that he had to study hard because he was destined for the throne, it surprised him.
After all, he had an older sister, and everyone always made a fuss over her. Plus his mother, Queen Victoria, was doing a fine job running the royal show.
"As a kid, he'd always just assumed his older sister was going to be Victoria the Second," says Carolyn Harris, a teaching fellow at Queen's University in Kingston, Ont., and an expert on British royalty.
"It had to be explained to this little boy a few times that it's you and all your brothers before it's your sisters."
Changes approved by Commonwealth leaders clear the way for women to inherit the throne on the same basis as men. No longer will a male heir take precedence over an older sister.
All that raises an intriguing question: What if it had always been that way?
"There's a lot of interesting what-ifs," Harris says.
Among them, would Henry VIII have even come to power (sparing a few wives their grief) and who would have been on the British and German thrones during the First World War.
As History Today editor Paul Lay wrote in the Guardian newspaper recently, Queen Victoria's daughter "also happened to be the Empress of Germany and Queen of Prussia and would have united the crowns of the greatest military and industrial powers of the age."
"Her son, Kaiser Wilhelm II, would have been King William V, the first and second world wars would never have happened and we would all be driving top-of-the-range Audis and embracing low levels of personal debt."
A different First World War?
Most intriguing of the what ifs, Harris suggests, and most recent is the case of Queen Victoria, who was on the throne from 1837 until 1901. Victoria's first child was her namesake daughter, and her second was the aforementioned Edward. The younger Victoria married Prince Frederick of Prussia, and their eldest son became Kaiser Wilhelm the Second of Germany.
Had he ended up on the throne of England and Germany, "one can assume World War I wouldn’t have happened the way it did," Harris says.
Mind you, she doubts it would have come to that.
"If Victoria had been the heir to the English throne, realistically they would have found her a different husband," says Harris, and not one who was the heir to another dynasty.
Dynastic marriage had been the way of the royal world for a while, but it was falling out of favour by that time.
"Dynastic marriage ceased to be as politically important with the end of the Napoleonic wars and the beginning of the 19th century," says Harris. "But throughout the 19th century until about the 1920s, there were only so many people that a member of a royal house could marry who were also royal."
If girls had equally inherited the throne, other intriguing possibilities emerge in the line of succession. Margaret Tudor might have followed her father, Henry VII, meaning her younger brother might not have become Henry VIII.
"Henry the VIII did have an older sister who was born between his eldest brother, who died, and him, and she became Queen of Scotland so one assumes Scotland and England would have been unified a few generations earlier," says Harris.
Or Henry VIII, who reigned from 1509 to 1547, might not have been so concerned about having a male heir — to the peril of a few wives.
"At the time Henry was reigning, there were no prohibitions against women ruling, but there also had never been a woman successfully take the throne and rule," Harris says.
"One of William the Conqueror’s granddaughters had tried and ended up in a 20-year civil war with her male cousin back in the 1100s."
Charles I, who reigned from 1625 to 1649 and ended up beheaded after being charged with treason, also had an older sister.
The succession changes in British legislation that goes back to 1689 will apply only to descendants of Prince Charles, current heir to the throne, and do not affect the existing line.
If the changes were retroactive, it would cause considerable juggling: for example, Princess Anne, who is older than her brothers Prince Andrew and Prince Edward but below them in the line of succession, would rise from her current position at No. 10 to No. 4, after Charles and Princes William and Harry.