The Tudor Reformation of the 16th century had never been completed. Within England these discontented groups of Catholics in 1605 had come close to destroying King and Parliament in the Gunpowder Plot. Meanwhile, the Protestant majority was increasingly fragmented over interpretations of the Bible and religious rights and observance.
Meanwhile, Scotland was divided between fundamentalist Protestants (Calvinists) and Catholics, while in Ireland a Catholic majority was governed by a minority of Scottish and English Protestants.
These divisions contributed to the start of the Civil Wars and persisted throughout the Interregnum.