First Cut: Double Lesson, Channel 4

If I'm being honest, I never saw the charm of Alan Bennett's Talking Heads. Too many quiet disappointments, too much capital-A Acting. They lacked naturalism in presentation and content, whereas Double Lesson, from Channel 4's First Cut series of quirky documentaries and quasi-documentaries, had naturalism to spare last night.

It probably helped that the show, a monologue given by Phil Davis to and across the camera, was based on real experiences of teachers who had attacked their pupils. Davis, playing David de Gale, explained from his potting shed, where he over-symbolically tended young plants, what had happened in the run-up to the attack.

His wife was having unpromising mammograms. He was directing a school production of Cat on a Hot Tin Roof, which the headmaster, presumably fearing that creativity sets children free, disapproved of. One pupil's brother had caused another teacher to hang herself, and now that pupil was throwing a rope around De Gale's neck.

Details were tormenting. The list of teachers' nicknames in the staff room served to warn and wear down the teachers. When the troublesome pupil's parents attacked De Gale at a parent-teacher evening, the son filmed it on his phone, a true child of the 21st century.

When De Gale described the moment before and when he plunged a compass into a pupil's shoulder, Davis was entirely compelling: he took you through it with sharp-angled tumult. The wearied looks on his face, the resignation, the sense of injustice even as he conceded the justice of the case - Davis excelled at making these fleeting or longer lasting, but always enduring. His delivery was not at all actorly but entirely in the patterns of natural speech.

Instead of Bennett's nugatory problems, writer and director George Kay took on modern society: the low esteem teachers are held in, the riot that pupils run, the bleeding of the personal into the professional, the internet and technology. The form may ultimately be artificial (documentaries normally use plenty of tricks to evoke the real), but Double Lesson showed why the well-executed monologue is worth preserving.

• Watch First Cut: Double Lesson on 4oD
• Find Talking Heads on Amazon