This post allowed him to develop a close personal relationship with the king which eventually bore fruit in the years following the downfall of his uncle.

The scandal at court was notable, given Villamediana's reputation as a caustic poet, who had made many political enemies and was implicated in a trial on sodomy.

At the death of the Count-Duke in July 1645 the title and inheritance of the counts of Olivares passed to Haro who came into the ownership of extensive landed possessions and of the dignity of grandee.

[4] Haro would never exert the same type of influence or control as his uncle had, mainly due to King Philip IV's reliance upon Sister María de Ágreda's counsel.

The alliance between Philip IV and France's first prince of the blood would become the central aspect of Haro's foreign policy until the Peace of the Pyrenees in 1659.

He was unable to avoid any perceived negative result of the treaty, nor was he able to reach an anti-French accord with the Lord Protector of the Commonwealth of England, Scotland, and Ireland, Oliver Cromwell.

Baltasar Gracián's Oráculo manual, José Pellicer's El Fénix y su historia natural and Juan de Espinosa Medrano's Apologético were dedicated to him.

'[16] Medrano credited Haro with restoring the Spanish Monarchy and praised his pivotal role in negotiating the Peace of the Pyrenees, calling him the "Archpolitician of the world.

"[16] Haro's foremost critics were the members of the party aligned with the papacy, especially the mystic Mary of Jesus of Ágreda and the Dominican theologian and philosopher John of St. Thomas, Philip IV’s confessor between 1643 and 1644.

[19] Among them were many of the most prized works in the collection, such as the Death of the Virgin by Andrea Mantegna, the Self-Portrait by Albrecht Dürer, La Perla by Raphael, The Virgin and Child between Saint Matthew and an Angel by Andrea del Sarto, The Washing of the Feet by Tintoretto, and Moses Saved from the Waters by Paolo Veronese, all of them currently in the Museo del Prado.

Haro purchased the large Christ and the Centurion by Paolo Veronese from Lady Alethea Talbot Howard, wife of the Earl of Arundel.