The Baron of the Chalk is the official ruler of a small sheep-raising region known as The Chalk, or sometimes The Wold, on the edge of the Ramtops below Lancre. His authority is maintained, in part, because there are too few subjects to get up a rebellion, and they're busy. He does maintain a small guard at the castle (Sgt Roberts, Kevin, Neville and Trevor with Old Robbins as night watch). The Baron has not been well for some years, and has been unable to exercise his usual control of his fiefdom. No one has noticed, really.
At the beginning of the events of I Shall Wear Midnight, the old Baron dies, transferring power to his son Roland, now 18 or 19 years old and with the experience gained fighting his scheming aunts for control during his father's illness. The new Baron is married at the end of the book to the unlikely and untrained Witch Letitia Keepsake. The ruling family's name is Chumsfanleigh (pronounced Chuffley).