Stephen Drew is what is politely referred to as "a character". Or, in the documentary-making world, "a gift".
When the camera first finds the deputy head at Passmores Academy, he is singing along loudly to Christmas pop songs. He pauses briefly mid-verse to accept a card from a pupil, and then starts up again.
Mr Drew is the subject of the first programme in a new series, Educating Essex, in which 65 fixed cameras capture daily life at a Harlow comprehensive. The cameras, therefore, see him striding down the corridors, leaving correctly uniformed pupils in his wake. "He's a little sergeant major character," says head Vic Goddard, before adding: "I'd be half as good a head without him."
This, it appears, is the standard perception of Mr Drew: half-comic caricature, half object of respect. "He's an evil overlord, who will completely incinerate you if you annoy him," says a bespectacled pupil. Then: "He's probably one of the best teachers in the school."
Recently, there has been a glut of school-based documentaries, most of which have focused on pupil misbehaviour, staff incompetence or systemic failings. Educating Essex, however, proves eminently more entertaining, purely by concentrating on genuinely compelling characters.
And so we see Mr Drew manage pupils with an endearing combination of humour, humanity and unbending insistence on the rules. For example, he tells recurrent miscreant Charlotte how to handle the teacher who accuses her of other people's crimes: "You say to her, 'I'm sorry that thing happened, Miss'."
Then - after assiduously polishing his own shoes - he patrols the corridors and catches sullen Carmelita in a red hoodie. He asks her to remove it, and she takes it off. But she refuses to hand it over. OK, Mr Drew says, he will just follow her around school instead, to make sure she does not put it back on. Carmelita is unimpressed: "You can just piss off."
No matter what pupils do, however, Mr Drew unfailingly sees the best in them. "I'm not going to blame Carmelita," he says. "She does the wrong thing. Fine. We move on. She makes her apology - eventually." Besides, he adds, he is more upset about the theft of his smoothie from the staffroom fridge at lunchtime.
"I like young people," he says. "I find them interesting; I find them exciting; I find them invigorating. Yes, it's hard work. But why is hard work a bad thing? Hard work is surely what makes people better."