Circumstances changed suddenly when Henry died on 6 June 1217 after receiving a head wound from a tile which came loose while he was playing with other children at the palace of the
bishop of Palencia. His guardian, Count Álvaro Núñez de Lara, tried to hide the fact, taking the king's body to the castle of
Tariego, although it was inevitable that the news would reach Berengaria. Berengaria was aware that her former husband might claim the Kingdom of Castile for himself. Therefore, she kept her brother's death secret from Alfonso. She wrote to Alfonso asking that their son Ferdinand be sent to visit her, and then declared Ferdinand king on 31 August. Her elevation of Ferdinand to kingship has been considered her
abdication, but her biographer Miriam Shadis argues that Berengaria did not see it like that and notes that Berengaria continued to rule. On the other hand, according to Georges Martin, she abdicated to her son in 1217 and thereafter remained a politically influential queen mother.
Robert Bartlett mentioned both the view that she was merely a sovereign for a short time in 1217 and the view that she continued as a co-ruler with her son thereafter. After Ferdinand's acclamation, Berengaria continued to intervene in state policy, albeit in an indirect manner. Well into her son's reign, contemporary authors wrote that she still wielded authority over him. One example was how she arranged the marriage of her son with
Elizabeth (Beatrice), daughter of Duke
Philip of Swabia and granddaughter of two emperors: Frederick Barbarossa and
Isaac II Angelos of Byzantium. The wedding took place on 30 November 1219 at Burgos. Another instance in which Berengaria's mediation stood out developed in 1218 when the scheming Lara family, still headed by former regent Álvaro Núñez de Lara, conspired to have Alfonso IX, King of León and King Ferdinand's father, invade Castile to seize his son's throne. However, the capture of Count Lara facilitated the intervention of Berengaria, who got father and son to sign the Pact of Toro on 26 August 1218, putting an end to confrontations between Castile and León. In 1222, Berengaria achieved the ratification of the Convention of Zafra, thereby making peace with the Laras by arranging the marriage of Mafalda, daughter and heir of the Lord of Molina, Gonzalo Pérez de Lara, to her own son and King Ferdinand's brother, Alfonso. In 1224 she arranged the marriage of her daughter Berengaria to
John of Brienne, a maneuver which brought Ferdinand III closer to the throne of León, since John was the candidate Alfonso IX had in mind to marry his eldest daughter Sancha. By proceeding more quickly, Berengaria prevented the daughters of her former husband from marrying a man who could claim the throne of León. Perhaps Berengaria's most decisive action took place in 1230, when Alfonso IX died having designated as heirs to the throne his daughters
Sancha and
Dulce from his first marriage to
Theresa of Portugal, superseding the rights of Ferdinand III. Berengaria met with the princesses' mother and succeeded in the ratification of the
Treaty of Las Tercerías, by which they renounced the throne in favor of their half-brother in exchange for a substantial sum of money and other benefits. Thus were the thrones of León and Castile re-united in the person of Ferdinand III, which had been divided by Alfonso VII in 1157. She intervened again by arranging the second marriage of Ferdinand after the death of Elisabeth of Hohenstaufen. Although he already had several children, Berengaria was concerned that the king's virtue not be diminished with illicit relations. This time, she chose a French noblewoman,
Joan of Dammartin, a candidate put forth by the king's aunt and Berengaria's sister
Blanche, widow of King
Louis VIII of France. Berengaria ruled alone while her son Ferdinand was in the south on his long campaigns of the
Reconquista. She governed Castile and León with her characteristic skill, relieving him of the need to divide his attention during this time. ==Patronage and legacy==