This chapter considers King Charlemagne's performance as referee in theological debates at the Councils of Aachen and Frankfurt. It also focuses on the Visigothic conciliar tradition, with King Reccared (586-601) as its most significant proponent. King Reccared is most famously remembered for having initiated the conversion of the Visigoths, the heretical 'barbarians' who had invaded the Iberian Peninsula in the mid-fifth century, to Catholicism. The chapter considers the ways in which Reccared staged his conversion, aiming at gaining support for his deed and wishing to turn the event into a public display of the alliance between regnum and sacerdotium. He was not the first king to convert from Arianism to Catholicism, but he was the first ruler to elaborate and formalise his conversion, and that of his magnates, at a general Church council.