He served as Lieutenant of the Spanish Royal Guards, a noble courtier, and became a prominent conspirator during the reign of Philip V and Isabel de Farnesio.

Among the direct ancestors of Jaime Vélaz de Medrano, his grandfather Antonio Vélaz de Medrano, I Marquess of Tabuérniga (Labastida, 1637 – Spa, 1683) a prominent soldier in the reign of Carlos II, Knight of the Order of Santiago, Sergeant General of Battle, he held the position of governor of Nieuwpoort in West Flanders and who in 1680 carried out a curious diplomatic initiative when negotiating with the United Provinces of the Netherlands to crown himself prince of the island of Tobago.

He was a prominent sailor and soldier in the reign of Philip IV who fought in the Battle of the Dunes in 1639 and was Captain General of the Armada de Barlovento and custodian of the New Spain Fleet, but who betrayed the crown in 1648, going to France, for whose King made several corsair raids in the Caribbean.

[3] His great-great grandfather Antonio Vélaz de Medrano y Mendoza had served as a soldier in Naples and Sicily and would later become magistrate in the towns of Malaga (1609–12) and Cuenca–Huete (1612–14).

Don Jaime José Ignacio Velaz de Medrano led a court intrigue against King Philip V and Elisabeth Farnese.

This court intrigue, in the words of historian Pedro Luis Lorenzo Cadarso, was a whole series of conflicts that "pitted different sectors of the ruling group, understood both in the political and economic dimension, among themselves or against the superior authority.

This was the era when the Court was moved to Seville due to the frail health of King Philip V. During this time and in the subsequent years, numerous intrigues unfolded involving the monarchs.

Who sweat blood to be devoured by the insatiable rage of their ambition… The courts trade with justice; the servants of the Royal House suffer inclemency; the troops have been forced to miserable officers, full of work forced to extreme necessity, to the charitable pity of the bishops and convents; commerce suffers losses and scorn; not even the Church forgives such a voracious tooth.

[2] Jaime José Ignacio Velaz de Medrano concluded his speech with professions of loyalty, love for the king and the kingdom, humility, and devotion.

[2] Jaime Vélaz de Medrano’s support for Fernando VI over Philip V was not an act of treason or rebellion, it was a testament to his unwavering loyalty to the monarchy, his homeland, and the values of good governance.

Medrano planned to entrust this representation to Fernando VI in his own hand on the night of 5 December 1730, taking advantage of one of those occasions when he had access to the intimacy of the princes.

Whether out of loyalty or out of sheer lust for survival, Jaime Velaz de Medrano disguised the whole affair with the utmost naiveté, assuring that no one was behind his representation and that he did not even have the slightest intention of handing it over to the prince.

Although with cyclical crises, the sovereign was able to maintain her hegemonic position during the following decades until the death of her husband, becoming, de facto, the ruler of the Hispanic monarchy.

The failure of the attempt did not discourage those disaffected with the princely room, who continued to pull the strings of intrigue in order to bring about the desired change.

Filled with aspiration to unite and inherit important titles and lordships in the future, he wrote to the king of Portugal requesting him to "deign to intercede with His Majesty."

To sweeten the refusal to support his pretensions, Carbone had obtained from the sovereign the concession of a coastal aid to the Marquis, a little more than one thousand and five hundred doubloons of sixty reales.

The surprise of the sovereigns must have been monumental, as can be deduced from their response: "he does not understand how this delinquent could have treated his marriage (...) because, having been deprived of all communication and correspondence, the adjustment and other circumstances that are supposed seem implausible".

[6] Far from consenting, the monarchs sent D. Pedro de la Cueva, "of the council of His Majesty, his mayor of the crime of the Royal Chancery of Granada," to make an inquiry into the circumstances in which these negotiations had taken place.

As a consequence of all this, Philip V ordered to reinforce the imprisonment of the prisoner, to isolate him and to put behind bars the Alcaide who had facilitated the meetings between the marquis and the Fuente el Sol.

With a small problem: his future wife had been locked up in a convent until the matter of the royal refusal was resolved, which is why Tabuérniga convinced his future brother-in-law to take his younger sister, Petronila, to the Rock, since as he himself recognized "well, for the importance of our honor, it was the same to marry this sister as the other and, thus fulfilling the reason of state of our families, we did not lack the obedience of our sovereigns, well, for this lady, of course permission had been requested, their majesties had not denied it".

There Don Jaime Velaz de Medrano would find a place to live, in a country in the midst of a pre-war climate just a few months before the outbreak of the War of Jenkins' Ear with Spain.

In London, Tabuérniga saw his advantage over the ignorance of the British, he pretended to be a Grande de España (his descendants will actually enherit this title), an unjust victim of the Queen's despotic policies and, more importantly, a magnificent investment for the future given his intimacy with Prince Ferdinand, for whom, Medrano claimed, he had experienced all his calamities, and with whom he could negotiate, once he acceded to the throne, a lasting peace treaty uniting the two crowns.

[2] His personal charisma won him the friendship of the Prince of Wales, the heir to the throne of England, to such an extent that the latter granted him a pension of 400 pounds for his subsistence.

[2] In 1746, the Duke of Newcastle, then Southern Secretary and in control of British foreign policy, approached the Marquis of Tabernuiga and proposed that he go to Lisbon to open secret negotiations with Spain about a peace treaty.

[9] Nonconformist by nature, the Marquess Don Jaime Velaz de Medrano decided to take advantage of this proximity to spy on the Prince of Wales and his closest collaborators, passing the information he obtained to the Duke of Newcastle, one of the main British ministers.

[2] On 13 June 1749 Ensenada told Sir Benjamin Keene that the king had agreed to grant the Marquess: ...the same pension he enjoyed in England (...) as a temporary provision for him until he was employed in the Master's service.

[10] Despite efforts to secure a higher pension—including diplomatic maneuvers by the Portuguese ambassador—these attempts ultimately failed, leaving Medrano in a precarious financial situation.

This forced exile kept him away from the court and the levers of power, while he remained burdened by outstanding debts in London—particularly those owed to the gentleman Ossorio—for which he still hoped to receive continued support from the English pension.

The fact that he tried to exert epistolary pressure on certain occasions on Don Carlos de Arizaga, lieutenant of Fernando VI while he was prince, it is suspected that this personage, or even his superior, the Count of Salazar, were aware of his intrigues and encouraged them.

[2] When Jaime José Ignacio Vélaz de Medrano came of age, a long lawsuit began between him and his cousin, Andrea Narcisa, to obtain the Marquessate.