That hollow column on the right is a “priest-hole,” a hiding place for Catholic priests, who were hunted with Elmer-Fudd-like tenacity when Elizabeth took the English throne around 1560. A “papist” could be hanged for saying mass; converting a Protestant was high treason.
Fortunately, the priests had a Bugs Bunny in the shape of Nicholas Owen, a Jesuit laybrother who spent his life devising secret chambers and hiding places for persecuted Catholics. “Pursuivants” could spend as much as a fortnight fruitlessly tearing down paneling and tearing up floors while the priest held his breath a wall’s thickness away.
Ickily, some of these hidden priests starved to death.