Rowling tells how Harry Potter’s least favourite teacher was based on a former teacher of her own, whom the author ‘disliked intensely on sight’

JK Rowling has revealed that Dolores Umbridge, the witch who forces Harry Potter to cut the words “I must not tell lies” on to his hand, was inspired by a real person.

In an essay for her website Pottermore, released to mark Halloween, Rowling says the inspiration for Umbridge was someone “whom I disliked intensely on sight”. The novelist has not revealed the person’s identity, but did write that she had been her teacher “long ago ... in a certain skill or subject”.

“The woman in question returned my antipathy with interest. Why we took against each other so instantly, heartily and (on my side, at least) irrationally, I honestly cannot say,” Rowling continued, noting the woman’s “pronounced taste for twee accessories”, including “a tiny little plastic bow slide, pale lemon in colour”, which the novelist felt was more “appropriate to a girl of three”.

Umbridge is first encountered by readers in Harry Potter and the Order of the Phoenix, originally published in 2003, as Senior Undersecretary to the Minister for Magic. Later, she joins Hogwarts school as its new Defence Against the Dark Arts teacher. She has a fondness for fluffy pink cardigans and lace, and speaks in a “sweetly girlish voice”. But Harry compares the black velvet bow on the top of her head to “a large fly perched unwisely on top of an even larger toad”, and when she gives him detention for speaking out in class about the return of the wizard Voldemort, she makes him use a magical pen to write the lines “I will not tell lies”.

“Harry placed the point of the quill on the paper ... He let out a gasp of pain,” Rowling writes in the novel. “The words had appeared on the parchment in what appeared to be shining red ink. At the same time, the words had appeared on the back of Harry’s right hand, cut into his skin a though traced there by a scalpel.” In his review of the book, Stephen King wrote in Entertainment Weekly that “the gently smiling Dolores Umbridge, with her girlish voice, toadlike face, and clutching, stubby fingers, is the greatest make-believe villain to come along since Hannibal Lecter”.

“I have noticed more than once in life that a taste for the ineffably twee can go hand-in-hand with a distinctly uncharitable outlook on the world,” Rowling writes in her Pottermore essay, recalling a time when she shared an office with a woman fond of “pictures of fluffy kitties”, who was also “the most bigoted, spiteful champion of the death penalty”.

“A love of all things saccharine often seems present where there is a lack of real warmth or charity,” Rowling writes, adding that Umbridge was “one of the characters for whom I feel the purest dislike”, and that “her desire to control, to punish and to inflict pain, all in the name of law and order, are, I think, every bit as reprehensible as Lord Voldemort’s unvarnished espousal of evil”.

Rowling also revealed that Umbridge is a “half blood” – the daughter of a wizard and a non-magical person, or Muggle – a status frowned on by some wizarding families. Pottermore said this was “especially noteworthy because in the books Umbridge lies to bolster her own pure-blood credentials”.

Rowling has added a selection of background material to Pottermore for Halloween, to mark the launch of the fifth book in her Harry Potter series, Order of the Phoenix, on the website. These range from the history of wizarding prison Azkaban to a closer look at the magical creature the Thestral. The essays are the latest in a wealth of new material she has added to the site since it launched in 2011. These have included “live” reports by Ginny Weasley – now Ginny Potter – from the 2014 Quidditch World Cup, and an insight into life as an adult for Harry and his cohorts.