However, far from being criticisms, the descriptions are in keeping with the idea and history of a “spare”, born out of the system of succession, which has evolved with the monarchy over the centuries.
‘I have given the duke an heir and a spare’
In modern times, the “heir and a spare” quote is usually attributed to Consuelo Vanderbilt-Balsan, heiress to the wealthy and celebrated American family of industrialists, who became prominent during the Gilded Age.
Marrying Charles Spencer-Churchill, the 9th Duke of Marlborough, in November 1895, Vanderbilt gave birth to two sons, John Albert William Spencer-Churchill and Lord Ivor Spencer-Churchill.
When her second child was born, she is said to have declared that she had given the duke, to whom she was unhappily married, “an heir and a spare".
The effect of primogeniture on heirs and spares
When it comes to why it became important for a monarch to have a “spare”, it is necessary to look back more than 900 years to changes in the rules of British royal succession.
As soon as hereditary systems were established in society, monarchs were keen not only to have a healthy male heir, but also, in an era of high infant mortality and no modern medicine, to have an additional male child in case the eldest died.
Before primogeniture — the succession of the first son as heir and a consequence of the 11th century Norman Conquest of Britain — all sons of kings were considered as possible successors.
They were encouraged to fight over the throne until the strongest and most powerful emerged to claim it.
After primogeniture was established, it became common to send “spares” abroad to conquer their own territories and win their own titles, with the added bonus that their absence from England lessened any threat to the heir.
By the 16th century, amid global power struggles, colonisation and trade wars, monarchs stopped risking their spares abroad and kept them closer to home.
The trouble with being the spare
Throughout history, “spares” have often struggled to find their role, from King Henry III’s brother, the Duke of Anjou, who spent his life in his sibling’s shadow, to Princess Margaret, who allegedly lamented her sister Elizabeth joining the line of succession, saying: “Now that Papa is king, I am nothing.”
The development of the role of the modern “spare” has been attributed to Prince Philippe of France, the younger brother of King Louis XIV of France, the Sun King who ruled from 1643 until 1715.
Philippe revelled in the freedom being a “spare” gave him, eschewing politics entirely and immersing himself in the arts to become a patron, advising his brother on topics including literature, art and culture.
In Britain, from the 17th century onwards, the “spare” joined the armed forces, acting as a royal representative with Queen Elizabeth II’s second son Prince Andrew joining the Royal Navy and Prince Harry serving in the army and RAF.
"There's nothing worse than going through a period in your life where you're making a massive difference and then suddenly, for whatever reason it is — whether it's media or the public perception of you — you drop off,” Harry told The Sunday Times in 2016 of his role in the royal family. “You want to make a difference, but no one's listening to you.”