In England, during the reign of Elizabeth I, laws were passed forbidding Catholics to celebrate their faith. Any found disobeying these laws were put to death for treason. This led to many old Catholic families in the country constructing concealed chapels within their large homes where Mass might be conducted in complete privacy. Adjacent to the chapel there would be a ‘priest hole’. This would appear as storage cupboard, a pillar, floorboard, or wall panel, but in fact provided a place where the officiating priest could run and hide should the priest-hunters arrive.
Priest-hunters would carry out thorough checks of the premises, which included the taking of measurements, sound checks, and the pulling down of suspicious parts of the house. A search could last weeks whilst the object of the priest-hunters’ desire lay silently within their hole. It was not unheard of for priests to die of starvation or lack of oxygen in these circumstances. The priest-holes were also used by cavaliers during the English Civil War.
Images 1 and 2 show a cupboard-come-priest-hole at Salford Prior Hall. 3 shows a priest-hall at Ufton Hall. 4, a stairway at Boscabel in Trent reveals the entrance to a handy hiding place, and 5, this wall panel in a summer house in Salisbury was discovered accidentally when:
one of the panels was found to open, revealing what appeared to be an ordinary cupboard with shelves. Further investigations, however, proved its real object. By sliding one of the shelves out of the grooves into which it is fixed, a very narrow, disguised door… can be opened. This again reveals a narrow passage, or staircase, leading up to the joists above the ceiling, and thence to a recess… In this there is a narrow chink or peep-hole. [Source]
[Sources: Images from Secret Chambers and Hiding Places by Alan Fea | Priest-holes]