 diplomatic and ecclesiastic, relations with their southern neighbours – for example the Normans' fealty to King Charles III of West Francia in 911.The concentration on ecclesiastic centres, which presumably housed vast amounts of movable wealth, has led some historians to believe that contemporary source writers, i.e.clergymen – including Prudentius and Hincmar, which are believed to have had at least editorial influence on the annals – exaggerated their accounts of the raids because they were usually the invaders' primary targets and frequently had to foot the bill when kings agreed to pay the Vikings off, as Charles the Fat did at the Siege of Paris in 885-6.