Constance was born in 1354 as the daughter of Peter, King of Castile and León and María de Padilla. The Infanta was born into a strange family dynamic- her parents had been married but in secret. The young king was under the control of his mother during this period, and he was coerced into denying he ever married María in order to marry Blanche of Bourbon instead. The relationship between Peter and Blanche was unsuccessful, however, and he kept María as his mistress for many years, having four children with her in total. The eldest child was Beatrice who became a nun, followed by Constance, then a sister Isabella who became Duchess of York and finally a son Alfonso who died as an infant. While Constance was technically illegitimate, she was not treated as such and was named as her father’s heir after the death of her brother.
As with many medieval princesses, we have little detail of Contance’s childhood, and we next hear of her at the time of her marriage when she was around sixteen years old. Constance’s marriage came about after a drawn-out period of war; her father had been involved in wars with Aragon from 1356, and then the Castilian Civil War also began in 1366. During this period, King Peter was known as a cruel ruler and was eventually overthrown by his half-brother Henry of Trastámara. In order to see himself restored to the throne, Peter and his daughters fled and Peter sought aid from Edward, the Black Prince who was the son of King Edward III of England. Luckily for Peter, Edward, the Black Prince agreed to help and decided to take his brother John of Gaunt into battle with him. It is said that Constance and her sister Isabella were given over to the English as collateral for huge loans that King Peter had taken out and would not be able to pay back.
The Black Prince and John of Gaunt helped Peter to defeat his usurping brother Henry. Peter was briefly restored to his throne, but the English princes then backed out of the war due to lack of payment. Ultimately after a long, complicated war, King Peter was killed by his half-brother Henry who claimed the throne of Castile for himself, ignoring Constance’s claim. Constance and her sister Isabella were still in English hands and were placed into dynastic marriages- Constance would marry John of Gaunt and Isabella would marry Edmund of Langley, 1st Duke of York. Both of these marriages were to sons of King Edward III and were suitable matches considering the girls were daughters of a deceased former king, but the teens must have been afraid of what lay ahead; being sent to England into marriages in order to pay off old debts.
Constance, the ‘de jure’ Queen of Castile, married the recently widowed John of Gaunt on 21 September 1371; the wedding took place in Roquefort, France. It was not until the following year that Constance travelled to England where she was given a ceremonial entry befitting the rank of a Queen – despite her not really being a Queen. Constance was escorted by her brother-in-law Edward, the Black Prince, and her ambitious new husband John started to go by the title of King of Castile and León.
Shortly after his marriage to Constance, John began an affair with a woman called Katherine Swynford. This affair lasted for decades, and it seems that Constance was forced to accept her husband’s relationship with Katherine. In the following years, Constance gave birth to a son named John and a daughter named Catalina or Catherine. Baby John only lived for a year, but Catalina survived the perils of medieval childhood.
Ever since his marriage to Constance, John of Gaunt had aimed to truly claim his wife’s lands in Castile and the Castilian crown, but due to lack of funds, he could do little but sit and wait. His opportunity finally came in 1386 when England and Portugal became allies. The treaty was formalised when John of Gaunt’s eldest daughter Philippa married John, the King of Portugal. The new allies soon requested aid in a succession crisis and John headed out to assist King John of Portugal. The son of Henry of Trastámara, also named John was trying to take the Portuguese throne too, and the Portuguese king needed assistance.
John of Gaunt travelled into Galicia, Castile with over 5000 men and his whole family. It seemed he might actually take the throne of Castile after all. However, the Castilians mostly refused to engage in battle, and John was lacking in finances for prolonged warfare. His troops were left starving and scavaging for food. Due to the terrible conditions, many soldiers and friends of John died or fled, and he was forced to sign a treaty with John of Trastámara. The Castilian king agreed to pay a large sum each year to John of Gaunt as long as John renounced his claims to the throne of Castile for good, this was agreed, and Catalina, the daughter of Constance and John, was given in marriage to John of Trastámara’s son Henry, meaning that at least Constance’s daughter would one day be the Queen of Castile.
On 24 March 1394, Constance passed away at Leicester Castle. She was buried in Newark Abbey. Following her death, John of Gaunt married his mistress Katherine Swynford, and their children were legitimised- this line led to the birth of King Henry VII of England whereas Catalina of Castile’s line would lead to the birth of Catherine of Aragon, Queen of England, both hugely important figures in European history, without the marriage of John of Gaunt and Constance of Castile, British history could be very different!