"One hand on the button, one hand to wash yourself with," the games teacher at my all boys secondary school would bellow as we shy educational detainees shivered in the chilly prison block hell that was the narrow corridor of open-plan showers.
Like all good PE teachers he was Welsh, built like stacked pill boxes, had the temperament of an army drill sergeant whose wife and children had just been insulted, and yelled with a monotone bark. He was the bulging-veined cherry on the crapcake that was the formative boys' changing room experienced by most of us with the XY chromosome.
We'd shuffle in from a gruelling cross country in the hail, lathered in mud, sweat, blood and snot. Scumming it all day by dodging the showers was not an option: any sign of dirt would mean being made to undress in front of everyone who'd already changed and march into the shower.
Back then it felt like the worst it could possibly get. So it's with horror that many of us will read about what happened at Thorpe Hall School in Southend.
For more than a decade, the school's deputy respected head Martin Goldberg was a secret peeping Tom who spied on young boys in the changing rooms by secretly filming them. It's a sickening abuse and a shame he's not alive to face justice: he killed himself while under police investigation. Hopefully the victims of his disgusting violation get any support they need.
This is the extreme end of the boys' changing room nightmare. And, fortunately, rare. But the words "boys' changing room" attached to this ugly story will evoke wince-inducing memories of much more common experiences.
It's ingrained within British culture to consider the boys' changing room a sinister place. They were hunting grounds for hyper-developed alpha boys, who looked like silver-back gorillas at 14, in which they stalked lesser pubescent prey. The rest of us were smooth, fleshy punchbags sprouting the odd face pube, who nervously masked our obvious youth behind towels, more often than not failing to master the awkward art of putting on boxer shorts while keeping your old chap hidden.
Similar scenes are played out across gritty British cinema. How many men can sympathise with young Billy Casper in Kes, who gets a verbal shoeing from PE teacher Mr Sugden over yet another lesson in which he's got no kit, before being made to get changed in front of baying classmates into an absurdly large pair of shorts?
And who can forget the Borstal bathroom violence in Scum, when Ray Winstone's character Carlin wraps a snook around the head of unsuspecting Banks as he washes in the sink? "I'm the daddy now," echoes Carlin's primal grunt as he hoofs Banks in the crotch.
In the biography of his life, Boy, the author Roald Dahl recounts one of his own changing room ordeals when he boarded at Repton School. A senior pupil in the public school's hierarchy, WW Wilson, had taken umbrage at one of Dahl's comments.
"At once he rounded up half-a-dozen seconds and they hunted me down. I ran into the yard where they cornered me and grabbed hold of my arms and legs and carried me bodily back into the 'house'," Dahl recalled.
"In the changing room, they held me down while one of them filled a bath brimful of icy-cold water, and into this they dropped me, clothes and all, and held me in there for several agonising minutes. 'Push his head under water!' cried WW Wilson. 'That'll teach him to keep his mouth shut!'
"I choked and spluttered and half-drowned, and when at last they released me and I crawled out of the bath, I didn't have any dry clothes to change into."
But these are all how the boys' changing rooms used to be. Those built in the years before and after the second world war tend to have all the charm of Soviet gulag torture cells. Grim-tiling, poorly lit, cold, grubby. Metal pegs and wooden benches. The kind of dank chamber Saw could have been filmed in where nothing by misery lurked in the fog of shower steam, testosterone and knock-off Lynx from Kwik Save.
Changing rooms are, well, changing. New schools and leisure centres being built offer a much more welcoming environment for today's schoolboys. The Department for Education's own guidance for school premises ensures as much. It requires newly built changing facilities to "provide adequate privacy".
Those of us adult men who experienced life under the old culture of boys' changing rooms can only look on in envy at the new generation who won't know the circle of hell Dante didn't quite reach.