One of my favorite songs from the pioneering British death/doom metal band Cathedral is "Hopkins (Witchfinder General)". The song starts off with the very distinctive great horror actor Vincent Price introducing himself:
"My name is Matthew Hopkins, Witchfinder."
So, I assumed that it was just based on an older British horror movie, which is of course where the samples came from as well as clips in the music video.
I was unaware that Matthew Hopkins was a real person and held the self-made office of Witchfinder General around the mid 1600's in England. He was active from 1645 to 1647 and during that time, he and his associates were responsible for more hangings than anyone else in the previous 100 years.
Hopkins used a variety of methods to elicit confessions, even though torture was unlawful at the time. He would also cut the arm of an accused witch with a dull knife, and if they bled, they were considered to be a witch. He also used the swimming test to see if the accused would float or sink. It was a swimming test in name only though as the accused would be tied to a chair and thrown in the water. If they floated, the water had rejected them and they were a witch.
Hopkins wrote a book about his time as a witch hunter called The Discovery of Witches, which was published in 1647. Some of his methods were used in the Salem Witch Trials in the United States.