A particularly interesting example that demonstrates the unstable and calculating nature of arranging marriages of royal daughters was that of Isabella, eldest daughter of Edward III. Isabella defied all common stereotypes of a princess’s marriage by not becoming married until she was thirty-three. She also married a man much below her own social status, leading most to believe that she had married for love, especially unusual for the first marriage of an eldest daughter. However, her late marriage is not indicative of a lack of interest in her marriage prospects; she had a record number of betrothals and alliances proposed from the moment of her birth, although all were eventually unfruitful. Like most princesses, Isabella’s path to marriage began in the cradle.
Her first alliance was made when she was just three years old to the eldest son of King Alfonso of Castile.  This proposal was later given to Isabella’s younger sister Joan in 1344. The swapping of daughters for particular agreements was not unusual either, as kings navigated the most beneficial alliances at certain times. In Isabella’s case, Edward III still wished to retain a partnership with Castile, but his later proposals for her eldest daughter were deemed more politically beneficial. In the time between when Isabella was substituted for Joan, Joan had also been betrothed to Frederick of Austria in 1336, when she was four years old. The final negotiations were made for Joan’s marriage to Fredrick in 1341. Yet, three years later Joan had not left England as Edward continually stalled sending her to Austria. First, he stated that Europe was too dangerous for her to cross and then later claimed she needed to reach the age of consent before he sent her to her new home. Eventually, this alliance was dropped in favour of one with Castile, which was much more politically favourable. Furthermore, Edward attempted to arrange for Isabella to marry Louis de Male, the Count of Flanders in 1338, which was an even more politically advantageous alliance and hence why it was now given to the attention of the eldest daughter.
The negotiations over this union took over nine years to complete. The alliance would have bolstered Edward’s position against France. Eventually, in 1347, Louis agreed to the marriage, and he met Isabella, now aged fourteen. Their betrothal took place on the 14th March 1347 at St Vinoc Bergues. While the court was preparing for the celebration, the reluctant groom defected to the French court, and the marriage proposal was nullified by the Count’s marriage to Margaret of Brabant later that year. Barbara Tuchman suggests that this event greatly humiliated both Isabella and her father and explains why Isabella’s later proposal with Bernard d’Albret of Gascony failed. However, before this Isabella was betrothed twice more. While the negotiations were happening with Flanders, Edward arranged for Isabella to marry the son of the Duke of Brabant. In 1344, he requested a papal dispensation to ignore the rules of consanguinity as Isabella and the Duke of Brabant both descended from Margaret, daughter of Edward I. This alliance proved to be unsuccessful.
Edward also sought a union between Isabella and Charles IV of Bohemia in 1349; although it appeared that they were not interested in making an alliance. Finally, in 1351 Isabella was betrothed to Bernard d’Albret, Lord of Albret in Gascony. Edward had prepared ships to take her across the channel, but Isabella refused to board them. Jessica Lutkin’s revaluation of this choice stresses that this was not an act of defiance by Isabella to exact revenge on her father for her humiliation at the hands of the Count of Flanders, as suggested by Tuchman’s analysis of events, but purely a political decision on behalf of Edward who no longer had anything to gain by the marriage alliance and was unwilling to lose his most valuable bargaining tool of an eldest daughter. Furthermore, Lutkin stresses that the marriage of an eldest daughter was an expensive event and Edward would rather use those funds to support his war effort. Green argues that overall Edward III was more lenient when it came to pushing his foreign alliances through the marriage of his daughters as he had seen the outcomes of his sisters’ unhappy marriages. His decision to allow his daughter to remove herself from the Gascony alliance is often seen as an indulgent act by a father to his spoilt favourite daughter. However, Ormrod argues, ‘Edward III attempted to harness the ambitions of his children by giving them direct vested interests in the policy of imperial expansion.’
He continually sought foreign matches for his children to further his control across Europe; only his youngest daughter Margaret married an English noble. The intricate web of negotiations and alliances forged across Europe by Edward III by the promise of marriage through betrothals to his eligible daughters exemplify the importance princesses held in international diplomacy. The core role of a royal daughter was to make an advantageous alliance with her marriage, especially if she was the eldest. Even without actually marrying his eldest daughter, Edward successfully made and withdrew alliances with four different states, through promises and marriage agreements for her hand. Although sometimes these agreements ended for reasons outside of his control, Edward successfully utilised these alliances to the utmost extent by delaying them or by manipulating them in his favour as the politics of Europe changed. Instead of being seen as unsuccessful as an eventual marriage contract was not reached in these cases, Isabella was an invaluable political tool for her father to create and break bonds with foreign states that were used for his political advantage.
 Calendar of Patent Rolls, Edward III, 1334-1338, p.133.
 ibid., 1343-1346, p.448.
 Calendar of Patent Rolls, Edward III, 1341-1343, p.245 and Edward III, 1343-1346, p.348.
 ibid., 1333-1337, p.678.
 Mary Anne Everett Green, The Lives of the Princesses of England: Vol 3, 1849-1855, p.181.
 Froissart’s Chronicles, Geoffrey Brereton, ed and trans., Middlesex, 1968, p.101.
 Barbara Tuchman, Distant Mirror: The Calamitous Fourteenth Century, New York, 1979, p.90.
 Green, Vol 3, p.178.
 Calendar of Patent Rolls, Edward III, 1348-1350, p.251.
 ibid., 1350-1354, p.114.
 Tuchman, pp. 205-206.
 Green, Vol 3, p.164.
 Mark Ormrod, Edward III, Yale, 2011, p.255.