Castile and Spain. Eventually, the Crown of Aragon, which then ruled Malta, joined with Castile in 1479, and Malta became part of the Spanish Empire. Meanwhile, Malta's administration fell in the hands of local nobility who formed a governing body called the Università. The islands remained largely Muslim-inhabited long after the end of Arab rule. The Arab administration was also kept in place and Muslims were allowed to practise their religion freely until the 13th century. The Normans allowed an emir to remain in power with the understanding that he would pay an annual tribute to them in mules, horses, and munitions. As a result of this favourable environment, Muslims continued to demographically and economically dominate Malta for at least another 150 years after the Christian conquest. In 1122, Malta experienced a Muslim uprising and in 1127 Roger II of Sicily reconquered the islands. Even in 1175, Burchard, bishop of Strasbourg, an envoy of Frederick I, Holy Roman Emperor, had the impression, based upon his brief visit to Malta, that it was exclusively or mainly inhabited by Muslims. In 1192, Tancred of Sicily appointed Margaritus of Brindisi the first Count of Malta, perhaps for his unexpected success in capturing Empress Constance contender to the throne. Between 1194 and 1530, the Kingdom of Sicily ruled the Maltese islands and a process of full latinisation started in Malta. The conquest of the Normans would lead to the gradual Romanization and Latinization and subsequent firm establishment of Roman Catholicism in Malta, after previous respective Eastern Orthodox and Islamic domination. Until 1224, however, there remained a strong Muslim segment of society. In 1224, Frederick II, Holy Roman Emperor, sent an expedition against Malta to establish royal control and prevent its Muslim population from helping a Muslim rebellion in the Kingdom of Sicily. After the Norman conquest, the population of the Maltese islands kept growing mainly through immigration from the north (Sicily and Italy), with the exile to Malta of the entire male population of the town of Celano (Italy) in 1223, the stationing of a Norman and Sicilian garrison on Malta in 1240 and the settlement in Malta of noble families from Sicily between 1372 and 1450. As a consequence of this, Capelli et al. found in 2005 that "the contemporary males of Malta most likely originated from Southern Italy, including Sicily and up to Calabria." According to a report in 1240 or 1241