Ceawlin of Wessex in 592, Æthelberht was the bretwalda, or leading Anglo-Saxon ruler; Bede refers to Æthelberht as having imperium (overlordship) south of the River Humber. Trade between the Franks and Æthelberht's kingdom was well established, and the language barrier between the two regions was apparently only a minor obstacle, as the interpreters for the mission came from the Franks. Lastly, Kent's proximity to the Franks allowed support from a Christian area. There is some evidence, including Gregory's letters to Frankish kings in support of the mission, that some of the Franks felt that they had a claim to overlordship over some of the southern British kingdoms at this time. The presence of a Frankish bishop could also have lent credence to claims of overlordship, if Bertha's Bishop Liudhard was felt to be acting as a representative of the Frankish church and not merely as a spiritual advisor to the queen. Frankish influence was not merely political; archaeological remains attest to a cultural influence as well. In 595, Gregory chose Augustine, who was the prior of the Abbey of St Andrew in Rome, to head the mission to Kent. The pope selected monks to accompany Augustine and sought support from the Frankish royalty and clergy in a series of letters, of which some copies survive in Rome. He wrote to King Theuderic II of Burgundy and to King Theudebert II of Austrasia, as well as their grandmother Brunhild, seeking aid for the mission. Gregory thanked King Chlothar II of Neustria for aiding Augustine. Besides hospitality, the Frankish bishops and kings provided interpreters and Frankish priests to accompany the mission. By soliciting help from the Frankish kings and bishops, Gregory helped to assure a friendly reception for Augustine in Kent, as Æthelbert was unlikely to mistreat a mission which visibly had the support of his wife's relatives and people. Moreover, the Franks appreciated the chance to participate in mission that would extend their influence in Kent. Chlothar, in particular, needed a friendly realm across the Channel to help guard his kingdom's flanks against his fellow Frankish kings. Sources make no mention of why Pope Gregory chose a monk to head the mission. Pope Gregory once wrote to Æthelberht complimenting Augustine's knowledge of the Bible, so Augustine was evidently well educated. Other qualifications included administrative ability, for Gregory was the abbot of St Andrews as well as being pope, which left the