overlordship could be established in a relatively short period. By the middle of the 8th century, other kingdoms of southern Britain were also affected by Mercian expansionism. The East Saxons seem to have lost control of London, Middlesex and Hertfordshire to Æthelbald, although the East Saxon homelands do not seem to have been affected, and the East Saxon dynasty continued into the ninth century. The Mercian influence and reputation reached its peak when, in the late 8th century, the most powerful European ruler of the age, the Frankish king Charlemagne, recognised the Mercian King Offa's power and accordingly treated him with respect, even if this could have been just flattery. Learning and monasticism (660–793) Michael Drout calls this period the "Golden Age", when learning flourished with a renaissance in classical knowledge. The growth and popularity of monasticism was not an entirely internal development, with influence from the continent shaping Anglo-Saxon monastic life. In 669 Theodore, a Greek-speaking monk originally from Tarsus in Asia Minor, arrived in Britain to become the eighth Archbishop of Canterbury. He was joined the following year by his colleague Hadrian, a Latin-speaking African by origin and former abbot of a monastery in Campania (near Naples). One of their first tasks at Canterbury was the establishment of a school; and according to Bede (writing some sixty years later), they soon "attracted a crowd of students into whose minds they daily poured the streams of wholesome learning". As evidence of their teaching, Bede reports that some of their students, who survived to his own day, were as fluent in Greek and Latin as in their native language. Bede does not mention Aldhelm in this connection; but we know from a letter addressed by Aldhelm to Hadrian that he too must be numbered among their students. Aldhelm wrote in elaborate and grandiloquent and very difficult Latin, which became the dominant style for centuries. Michael Drout states "Aldhelm wrote Latin hexameters better than anyone before in England (and possibly better than anyone since, or at least up until John Milton). His work showed that scholars in England, at the very edge of Europe, could be as learned and sophisticated as any writers in Europe." During this period, the wealth and power of the monasteries increased as elite families, possibly out of power, turned to monastic life. Anglo-Saxon monasticism developed the unusual institution of the "double monastery", a house of monks