The Willing Warlock is a minor character in Charmed Life who lives in the same village as Eric and Gwendolen Chant. He is known as someone who makes a fairly poor living doing odd jobs, both magical and nonmagical. He's a sturdy, muscular sort of person, and none too bright, it seems.
When he participates in a very dastardly attempt to kill and disable the civil servants at Chrestomanci Castle, he, along with the rest of his gang, is stripped of his magic, which is only fair.
Diana Wynne Jones later wrote a short story about him in which he decides to turn to a life of crime, and is thwarted at every turn by cars, dogs, and children in another world where he's unfamiliar with all the rules.