Londinium (modern-day London) in Britannia. In this way, Egyptian religion diffused into that of the Romans and enjoyed a wide range of worship all over the Mediterranean. Despite this, this intercultural diffusion almost certainly involved the modification (Hellenisation) of native Egyptian gods so that they were more palatable to converts. The form that Isis took among Greeks and Romans combined her Egyptian traits with Graeco-Roman ideas. Christianity enters Egypt The largest and oldest Christian church in Egypt, the Coptic Orthodox Patriarchate of Alexandria, credits its founding to Mark the Evangelist, AD 42. A considerable number of Jews resided in Egypt, and Alexandria specifically, with their residence in the country predating the first Christians by perhaps as long as 600 years. Scholars believe that downward social mobility of Jews in Roman Egypt made them more receptive to Christianity. In any case, Alexandrian Christianity began to grow rapidly starting from its very establishment. Under Pope Demetrius I, a bishop from AD 189 to 231, Christianity spread through Egypt up the Nile and increased its influence in the larger Church. Up until the Council of Chalcedon in AD 451, Alexandria was on par with Rome and Constantinopole as an influential Christian city. Diocletianic Persecution The Emperor Diocletian viewed Christianity as disrupting traditional Roman religion (and thus a greater threat to the solidarity of the empire), so he initiated a severe persecution of Christianity to attempt to curb its growth in the empire. Though this was not the first edict by an emperor against Christianity to affect Egypt (that being Septimius Severus in AD 202, when he dissolved the Catechetical School of Alexandria and forbade conversion to Christianity), the Diocletianic Persecution would be the most severe. In AD 303, Diocletian ordered all churches destroyed, sacred books burned, and enslaved all Christians who were not officials. This decree was in effect for three years, leading to the Era of Martyrs dating system later created by the Church of Alexandria, but many Egyptian Christians survived the persecution because they were instead sent to work in quarries and mines, as penal labour. Overall, however, the persecutions of Christianity were not successful anywhere in the Empire in ceasing its growth. Traditional religion was already beginning to suffer, even more so in Egypt, where Alexandria was an established and bustling centre for Christianity. Decline of paganism in Egypt Native Egyptian religion had at least a somewhat substantial effect on