The Demon Headmaster is a series of books by Gillian Cross which were later adapted as a television series starring Terrence Hardiman in the title role and Frances Amey as Dinah.

The title character is a strange being with the powers of hypnosis and a desire to take over the world, as he believes it will be better under his ordered rule. He has piercing light green eyes, which he normally hides behind dark-tinted glasses —- removing these in order to hypnotise his victims.

Very little about the Demon Headmaster or his background is shown in the books. His name is never revealed; he is referred to only as 'the Headmaster' both in the books and on television, except when he takes on an alias —- such as the Computer Director in The Prime Minister's Brain, for example; and on each occasion he uses a title rather than a name. It's revealed in-narrative that he does have a name (Brain has characters forced to add the name to a list of people allowed to visit the Prime Minister, and Takes Over involves the Headmaster's name as a plot point), but the name itself is never spoken by anyone.

• The Demon Headmaster - ISBN 0-19-275374-6
• The Prime Minister's Brain - ISBN 0-19-275372-X
• The Revenge of the Demon Headmaster - ISBN 0-19-275373-8
• The Demon Headmaster Strikes Again - ISBN 0-19-275388-6
• The Demon Headmaster Takes Over - ISBN 0-19-275389-4
• Beware of the Demon Headmaster - ISBN 0-19-275236-7 (a short story about the Demon Headmaster, without the other characters)
• Facing the Demon Headmaster - ISBN 0-19-275369-X
• Total Control - ISBN 9780192745750
• Mortal Danger - ISBN 9780192766069

First published in 1982.^[1]

Dinah Glass moves in with Lloyd and Harvey Hunter and at first, does not like them. Soon she discovers that at her new school, the Headmaster is very strange and she finds herself saying things like, "I think the Headmaster is a marvellous man and this is the best school I've ever been to". With the help of her new friends, SPLAT, (Society for the Protection of our Lives Against Them, the children at the school who are immune to the Demon Headmaster's hypnotic powers), she successfully stops the Headmaster's plot to hypnotise the country through the Eddy Hair Television Show and she gets adopted by the Hunters. This became the first three episodes of the first series of the television adaptation.

First published in 1985.^[2]

Dinah wins a place in the final of a computer competition, and she and SPLAT go to the finals. Little does she realise that the computer competition is a plot by the Demon Headmaster to take over the world, by hacking into the Prime Minister's computer (The Prime Minister's Brain) and hypnotising the Prime Minister, thus allowing him to meet the other world leaders and gain control of them himself. This became the last three episodes of the first series of the television adaptation. (Later republished as The Demon Headmaster and the Prime Minister's Brain following the success of the television series.)

First published in 1994. as "Hunky Parker is Watching You".^[3]

When Ingrid turns up at a SPLAT meeting she is raving about Hunky Parker, a new TV show. It is the latest craze, she says, and soon everyone will be hooked. The other SPLAT members disagree until Ingrid shows them her Hunky video, which Dinah eventually realises is due to subliminal messages in the tape. Tracking the source of Hunky Parker merchandise, SPLAT learns that it has been created by the Demon Headmaster, attempting to trigger riots for new merchandise that he can use to exert his control over the populace.

First published in 1996.^[4]

Dinah's father is headhunted for a new job at the Biogenetic Research Centre, unaware that the Demon Headmaster is the director. This time his lust for power sees him meddling with evolution itself. He has created an Evolution Accelerator: a machine to speed up the evolution process and produce the perfect human, beginning with the development of a fast-growing poisonous creeper that attacks Lloyd. But for this, he needs Dinah's DNA - combining it with a lizard to create Eve, a human/lizard hybrid who possesses Dinah's intellect but lacks her emotions - and then put her into terrible danger, pitting her against Eve to test his theories. This became series two of the television adaptation.

First published in 1997.^[3]

When the army starts dismantling the research centre, Dinah contacts Professor Claudia Rowe, an expert on botanical sciences who has expressed an interest in the creeper. Then weird things start to happen. Libraries start closing and their books are taken away. Telephones stop working, and there is no internet access. People start talking like robots, even Claudia Rowe, and more and more of the population seem to be wearing strange badges. Dinah's search leads her to the university where she finds the mysterious Director developing "Hyperbrain", a computer with superhuman intelligence and deadly potential. SPLAT swiftly realises that, although the original Headmaster was killed when he fell into the Evolution Accelerator, the machine still recorded his DNA and was thus able to create a clone, lacking the originals memories but retaining his lust for control. This became the third and final series of the television adaptation.

First published in 2002.^[5]

The new club Purple is the place to go - if one can get in - and Mandy's cousin, Ellie, persuades Dinah and her friends to come along too. The man everyone wants to see is DJ Pardoman whose face keeps changing from Elvis to Madonna to Brad Pitt. His electronic mask is mesmerising but no one knows who he really is. When the kids visit his website they find an online competition: the person who finds out DJ Pardoman's true identity will be allowed to lift off the mask. Dinah, thinking the whole setup strange, joins in out of curiosity. In her search she stumbles across something amazing: her real father might be alive after years of thinking he was dead. Dinah must find out more. But she only realises the truth of these strange coincidences too late. This time the Demon Headmaster is intent on ensuring that Dinah will not interfere with his plans.

First published in 2017.

The story continues with a new group of children, in a new school, without SPLAT's members. The stories centers on Lizzie, her younger brother, their friend Ethan and Angelika. Lizzie and her brother return from the United States, where their mother had surgery. After returning to their school, they realise that the school has a new headmaster and the students are showing exceptional talents, even their bully enemy Blake. However Lizzie suddenly starts to behave aggressive against the school, her brother becomes a robotics genius and their recent made friend Ethan becomes a soccer star. But when they try to talk, or even think about those sudden changes, their minds goes blank. Ethan eventually discover that the Headmaster is hypnotising and controlling everybody in the school. They team up with Angelika (a girl who suddenly became a coffee business enthusiast) and even Blake (who became a Multilingual greeter) and discovers the great plot of The Headmaster to show to the Prime Minister the great results of the school, thus allowing The Headmaster to administer other schools.

First published in 2019.

In 1998, Puffin Books released a series of goody bags on certain themes and featured a notepad, pencil, rubber, etc., along with a small book. In the 'Fantasy' goody bag there was a book calling 'Crash Landing & Other Stories' by Gillian Cross. This book contains three short stories about the Demon Headmaster or people similar to him.

The first story, called 'Crash Landing', is set at some point after The Prime Minister's Brain, and is about the Demon Headmaster crashing his getaway helicopter in a small village, although he is identified only as 'the Visitor'. It features SPLAT-type characters, including a lead named Charity who actually reads the Demon Headmaster books in the story, Charity defeating the Headmaster by using mirrored sunglasses to trick him into hypnotising himself.

The second story, called Carnival!, does not explicitly identify one of its characters as the Demon Headmaster, but from the illustrations and description are meant to make it obvious that it is him.

The third story is called 'Maths Homework', and features a teacher referred to as Old Webster. This is not the Demon Headmaster but is a very similar character. The introduction to the story says, 'Maybe you think you have spotted the Demon Headmaster somewhere. Are you sure? Things aren't always what they seem.'

In the front of the book it says that 'Crash Landing' was first published in Shark And Chips And Other Stories, and that 'Carnival' was published in the Young Telegraph in 1996. The third story is not mentioned.

Dinah is the main protagonist in the story The Demon Headmaster by Gillian Cross. She arrives in the story at the Hunters' house as a foster child, having been orphaned at an early age and brought up in a children's home. She is extraordinarily intelligent, but she normally keeps this quiet. Her intelligence causes the Headmaster to take an interest in her, and makes her pivotal in his plans to win a national school quiz competition for nefarious ends, as well as other subsequent plots, made easier by the fact that she is the only member of SPLAT not immune to his hypnosis. At the end of the first story, Dinah is adopted by the Hunter family and becomes Dinah Hunter.

He is son of Mr and Mrs Hunter. He is the founder and leader of the Society for the Protection of our Lives Against Them, or SPLAT as it is known. Lloyd is one of only five children in the entire school whom the Headmaster is unable to hypnotise. Lloyd comes across as arrogant and cocky at times and also is not the brightest kid at school unlike his now proper sister, Dinah, but Lloyd has shown on more than one occasion he is by no means stupid and is a more than capable leader of SPLAT even though he does come across as bossy and hates people stealing his thunder. Lloyd at first is very hostile towards Dinah and also takes the longest to accept her out of all the members of SPLAT, but eventually he is the first to suggest that his and Harvey's parents adopt Dinah. A standing joke within the stories is Lloyd's tendency to make loud alliterative exclamations when annoyed or surprised, typically involving strange-coloured foodstuffs - e.g. 'Black bananas!'

Harvey is a pleasant laid-back boy, very different to his older brother, Lloyd. It is clear he is very close to Lloyd, possibly because Lloyd has always looked out for him at school and helped him stay out of trouble with the Headmaster. Harvey accepts Dinah into the family and SPLAT a lot quicker than Lloyd and the others do, and soon is as close to his new sister as he is his brother. Harvey seems to understand Dinah more than Lloyd does and is more prepared to listen to her.

Ian acts as Lloyd's second-in-command in SPLAT. Ian, like Harvey, is very laid back and very much the joker of SPLAT. Ian will often break any tension with a well-timed joke and acts as a good foil to the more serious Lloyd.

Mandy is one of the more mature members of SPLAT and seems to be the motherly influence in the society. She is the best at soothing people like Lloyd and Ingrid when they get in a temper, and is generally the most level-headed of the gang, although she is not above making the odd snide remark when Lloyd's plans backfire.

Ingrid is the youngest member of SPLAT, but she is no pushover. Ingrid is generally the most childish member of SPLAT, prone to sulking when things do not go her way or the others do not listen to her. The fact that she is the youngest does mean that she is generally ignored if she makes a suggestion

The Headmaster is the main antagonist of the series. He can turn almost anyone into a hypnotic state by having them look into his eyes, except for a few who seem to be naturally immune, among them Ingrid, Mandy, Harvey, Lloyd and Ian. He has a fixation with order and control, attempting to eliminate chaos even if that means basically depriving people of emotion, and has demonstrated a strong desire to enforce that control on others. In the course of the novels he has either established or infiltrated such diverse organisations as a school, a computer lab, a television studio, a genetics research facility, a university, and even a night club, with the goal of using his contacts in these businesses to enforce his will on the world. The original Headmaster was killed at the conclusion of The Demon Headmaster Strikes Again when he was forced into his own evolution accelerator machine by a fast-growing creeper he had created, but the machine was later accidentally activated to create a clone of the Headmaster, who was able to learn about the world from the material in the research centre but lacks any of the original's personal memories. As a result, the 'new' Headmaster retains the original's desire for control and hypnotic abilities, but completely failed to recognise Lloyd, only identifying Dinah as an associate of the original Headmaster because he found a video recording of her talking to his 'predecessor'.

In 1996, the Demon Headmaster books were adapted by the BBC to make a television series based on the books, starring Terrence Hardiman in the title role. For the show, the Headmaster's glasses were changed from the dark-tinted ones he wore in the books to blue-tinted.

The series proved popular with children and ran for three series from 2 January 1996 to 22 January 1998. The first series contained six episodes, and aired twice weekly from 2 to 18 January 1996, the second series contained seven episodes, and aired once a week from 25 September to 6 November 1996, and the third series contained six episodes, and aired twice weekly from 6 to 22 January 1998.

The first series of the show was split into two distinctive story lines, with the first three episodes adapted from the first book in the series "The Demon Headmaster" and the last three were adapted from the second book "The Demon Headmaster and the Prime Minister's Brain". The second series was adapted from the fourth book "The Demon Headmaster Strikes Again". The third and final series was adapted from the fifth book "The Demon Headmaster Takes Over".

In 2019, CBBC broadcast a new adaptation, later revealed as a sequel to the previous show, from the book Total Control. It aired from Monday 14 October with the pilot episode, everystudentastar, adapted and showrun by Emma Reeves. Terrence Hardiman returned as the original Demon Headmaster in the first season's final episode, where he forced his 'successor' (Nicholas Gleaves) to stand down when their plans were thwarted — albeit only appearing as a hologram of himself rather than in person.

Reeves has pitched a second series to CBBC, using further elements of Total Control, as well as its sequel, Mortal Danger.^[6] A second series has since been confirmed,^[7][8] however ultimately, due to the delays caused by the COVID-19 pandemic it was cancelled.^[9]

All of the original books in the series were released on audiobook, although are now out of print. Most of the books in the series were read by Judy Bennett, although Facing the Demon Headmaster was read by Kelly Hunter and not Judy Bennett. Also The Demon Headmaster (the first of the series) was read by Terrence Hardiman and released on cassette.

The newer stories are narrated on audiobook by Steven Crossley.

• The Demon Headmaster at IMDb 
• SphereTV - Demon Headmaster at the Wayback Machine (archived 10 October 2007)