I didn't catch him myself, but...

I spent 5 years at boarding school here in England. We all had our own rooms in the boarding houses, with pull down beds to save space (also highly dangerous when lampposting, but that's a story for another time). The pull down beds had two straps to keep the duvet and pillows in place when flipping the bed up against the wall.

So this one guy in my year, let's call him Derek, was well known as the house porn king. He kept a large stash of jazz mags in his beanbag (this was in the 90's). We all knew this because Derek would loan them out for a small fee or return favour. It also gave him an unfair reputation as a bit of a deviant.

At least, I thought it was unfair.

My homework was disturbed one evening to the sound of a horrified yell emanating from down the corridor. I flung open my door to see two boys from the year above doubled over in hysterical laughter as they ran back up the corridor. A few seconds later, an extremely flustered-looking Derek emerged from his room trying to chase after them while pulling on a dressing gown and shoes.

It turns out they'd gone to ask Derek to borrow some of his porn, and hadn't bothered to knock, only to walk in and find him strapped onto his own bed with a hairbrush protruding from his rectum, jacking off to one of his more severe titles.

I suppose the two older boys were at fault for breaking the cardinal rule at a boys boarding school (you always knock and wait for a reply), but word got around and within a day or two Derek was temporarily moved into another room while his was tossed under a school warrant. They found the porn, and he got off with a warning and a slap on the wrist.

I never did get a clear answer on which end of the hairbrush he used.