According to the Catholic Encyclopedia, the founding of the diocese dates back to Francia,[REF] when St. Ecgberht of Ripon sent St. Willibrord and eleven companions on a mission to pagan Frisia, at the request of Pepin of Herstal [REF].
"Even though approximately one third of the people remained Roman Catholic and in spite of a relatively great tolerance,"[REF] as early as 1573,[REF] the public exercise of Catholicism was forbidden,[REF][REF] and the cathedral was converted into a Protestant church in 1580 [REF].