In 1641, the House of Commons ruled that every member should make an oath of allegiance to the King and to Parliament.
They then had to go back home to their own parish where any two of them were to require the same oath of allegiance from all males over the age of 18. The names of all who refused to make the oath were to be noted and assumed to be Catholics.
We have, in the Devon Protestation Returns, a set of amazing documents - something akin to a census even though no women or children are named. A transcription is available in the West Country Studies Library in Exeter.
But the Devon documents are not complete. Some were never returned, some places mentioned below had not yet acquired parish status, others were damaged or destroyed as the years went by - crumbling to dust in wooden chests stored in damp churches. These are the Devon Parishes for which, sadly, there are no recorded returns: