James Perez was the natural son of Peter III and the Lady Maria, and his rise to power within the court appears to have been rather rapid. In 1279, the king made him lord of Segorbe and sometime after that he was made admiral of the Crown of Aragon. He does not seem to have been overly concerned with his personal finances for in April 1283 Prince James ordered the people of Segorbe to pay off a debt incurred by Perez. This was not the first time that James Perez left others to pay his debts. As admiral of the fleet, he does not figure prominently in the preparations for the campaign planned against Tunis. Orders for men and material sent to various parts of the Crown of Aragon were issued directly by the king and omit any mention of James Perez. Sometime during 1280 James Perez was assigned the title of admiral. There is no extant document concerning the appointment, but he is mentioned as admiral of the fleet in a document dated July 1, 1280.
It is clear that early on the king did not have great confidence in James Perez. Prior to the Battle of Nicotera, actual command of the fleet was given to Peter of Queralt and Vice-Admiral Cortada. The king's lack of confidence proved well-founded when Perez grossly mishandle a raid into Calabria that resulted in troops being drowned and a group of the highly prized almugavers being stranded in enemy territory. The final straw appears to have been during this raid on Catona his inability to control a group of almugavars who murdered the Count of Alençon, who was the nephew of the king of France and the brother of Charles of Anjou.
Besides his ineptitude in conducting a naval operation, James Perez may have been removed from office for malfeasance. A great deal of money passed through the office of the admiral, and on taking command of the fleet in April 1283 Roger of Lauria had to account not only for his activities and expenditures, but also those of his predecessor. During his time in office Perez had collected 588 ounces of gold from prize money accrued from captured ships and goods. Apparently, he had failed to turn the money over to treasurer before leaving the office, for Roger was forced to cover the shortfall in money owed the crown with his personal funds.
That Peter III replaced James Perez with Roger of Lauria says as much about the king as it does about Perez. Charles of Anjou made most of his appointments concerning the fleet based on political or familial considerations. Despite the obvious inexperience of his own son Charles of Salerno, Charles of Anjou left him command at Naples, much to the determent of the fleet at the Battle of Naples in 1284. In a time when nepotism was more the rule than the exception, it is to Peter III's credit that when his own son proved inadequate, he did not hesitate to replace him.
James Perez would virtually disappear from any fleet activities, except for occasionally providing armed men to the fleet. However, he would be a constant irritant to Roger of Lauria. The Archive of the Crown of Aragon holds numerous orders from Peter III, Alfonso II and James II for James Perez to stop raiding Roger's property and to cease interfering in his affairs and duties as admiral.
