Who is the head teacher of the fictional school Crunchem Hall in Roald Dahl’s novel "Matilda"?

Agatha Trunchbull, also known as Miss Trunchbull or simply The Trunchbull, the fictional headmistress of Crunchem Hall Primary School (or Elementary School), is the main antagonist in Roald Dahl’s 1988 novel "Matilda", in the 1996 film "Matilda" and the 2011 musical "Matilda". She is said to look "more like a coked up chimpanzee and rather bloodthirsty follower of the stag-hounds than the headmistress of a nice school for children".

Miss Trunchbull is depicted as a "gigantic holy terror, a fierce tyrannical monster who frightened the life out of pupils and teachers alike" notorious for her brutal and wildly idiosyncratic discipline: trivial misdeeds (including simply wearing pigtails) incurring punishments up to potentially-fatal physical discipline. Her hatred of children is so great she denies ever having been a child herself.