(Photoof a priest hole by Quodvultdeus)
When she became Queen of England in 1558, Elizabeth I ramped up the suppression of Catholicism in her country. This did not deter many Catholics from adhering to their faith privately. Any Catholic priest was automatically wanted for treason against the Crown, so it was necessary to hide them.
The result was an architectural feature that has come to be known as the priest hole. It's a hidden chamber in a house where a priest could slip into and remain while priest hunters searched. Eric Grundhauser writes at Atlas Obscura:
These small hideaways were often built under staircases or inside fireplaces or behind false walls. (Even if you weren’t harboring a religious fugitive, the priest holes made a great place to stash your candles, crucifixes, and other Catholic accoutrements.) Some homes would have multiple priest holes scattered throughout, with at least one, Hindlip Hall, maintaining 12 separate holes. Some priest holes would even be hidden behind secret panels in other priest holes as an added precaution. The hiding places were generally very small, with barely enough room for a full-grown adult to fit, but they did the trick.
A Jesuit priest named Nicholas Owen was among those priests in hiding. He was also a master architect who helped build excellent priest holes. He paid the ultimate price for his devotion:
Owen was almost found out a number of times during his career, and got arrested and tortured in 1594. But even when subjected to agony, Owen never gave up the location of another priest or the holes he built. When was caught a final time in 1606, he gave himself up to distract from other priests hiding in the house. He was taken to the Tower of London and tortured to death, never giving an inch. For his work in creating the priest holes that saved countless lives, Owen was sainted by Pope Paul in 1970, and is now known as the patron saint of illusionists.