Of the Jews in royal service at this time the most influential by far was Judah aben Lavi de la Cavalleria. The family derived the surname “de la Cavalleria” from the fact that one of its ancestors at one time enjoyed the protection of the Order of Knights Templar. From 1257 on Judah appears as bailiff of Saragossa. In 1260 he was authorized to collect all the state revenues and to make all the necessary expenditures on behalf of the crown. All the bailiffs in the kingdom were required to turn over to him or his deputy all their collected monies along with their accounts. He had the right to discharge incompetent officials and appoint others in their steed. He was accountable directly to the royal chancellery. In 1263 Judah made available to the king a large sum of money to outfit a fleet against Moslems and during subsequent campaign against Murcia provided the means, which enabled the king to garrison border strongholds of Valencia with sufficient troops. He advanced the king money for his military and political needs on several other occasions. He finally became bailiff of the province Valencia, where he acquired land and herds of sheep. He was a man of influence also in his own Jewish community of Saragossa. This brought him into conflict with the aristocratic Alconstantini family, which, as we have seen, aspired to authority not only in Saragossa but over all the Aragonese aljamas.
During the latter part of James reign, Benveniste de Porta (died 1268) appears as one of the most prominent personalities in Catalonia. He served as bailiff of Barcelona and sometimes also of Gerona, Perpignan and Lerida. He also leased the mint at Barcelona. Astrug Jacob Xixon served as bailiff of Tortosa and nearby localities and in parts of the kingdom of Valencia north of the Jucar river. In the city of Valencia he owned a bakery, flour mills and baths. A native of Valencia, Vives be Joseph ibn Vives, was in charge of a number of rural bailiwicks in that kingdom. He also had command of the royal citadel in the city of Valencia and directed its defense during the Moslem uprisings in 1271 and 1280.
A number of other Jews served the crown in a variety of administrative posts. Yet even during the reign of James I the first symptoms of a growing tendency to eliminate Jews from public office could be noticed. In Catalonia, Jewish participation in the public administration increased remarkably up to the middle of the thirteenth century, but thereafter it declined steadily. Benveniste de Porta was the last Jewish official in Barcelona. In Aragon Jewish influence remained undiminished and even spread to the kingdom of Valencia, royal assurances to the contrary, given to the citizens of Valencia in 1251, notwithstanding. This new territory, populated predominantly by Moslems, was indeed of colonizing initiative, and the services of Jews could not yet be dispensed with. But during the reign of James" successor, Pedro III, the forces which eventually brought about the exclusion of Jews from public office became more powerful and more effective.