Bonner's coalhole

Occasionally in the sermons and writings of Charles Spurgeon you will find references to "Bonner's coalhole." It appears that this was an underground dungeon into which many Protestants were crammed during Queen Mary's reign. It was named after the Catholic Bishop of London, Edmund Bonner (called Butcher Bonner or Bloody Bonner). When Queen Elizabeth came to power, Bonner found himself thrown into the very prison that he has used against the Protestants.