Fossie's husband here. Regarding the Daily Mail article
www.dailymail.co.uk/news/article-2644715/St-Pauls-prep-school-betrayed-generation-Sinister-swimsuit-inspections-Senseless-beatings-Casual-cruelty-For-time-ex-pupil-lifts-lid-70s-regime-schools-investigated-sex-abuse.html
I was a day-boy at Colet Court and St Paul's in the 1970's and most of this is news to me! It's not some isolated fortress country school, it's in the middle of the SW London suburbs! Some masters were a bit high-IQ-weird, I admit, but there was never the slightest sexual interference that I ever witnessed.
If anything like this did happen, it must have been after-hours and confined to the boarding houses (2 out of 3 now replaced with music rooms), which only about 1 in 6 of Paulines attended then, far fewer now - most boys being entirely normal and well-mannered suburban day-boys with a grammar-school-on-steroids mentality and very keen for any excuse whatsoever to meet up with our friends' sisters (usually from Godolphin, as SPGS girls kept themselves to themselves).
Mr White was my teacher for a year at Colet Court and the only physical discipline of any kind that I remember was to myself because I was daydreaming, he'd asked me a question, repeated it, and was able to walk up to me and give me a gentle but firm slap on the cheek to wake me up before I even realised he was there! So although that's beyond what would be acceptable today, there was no damage done and it had a very lasting positive effect on my attitude!
I do remember at SPS that some of the loud-mouthed older rugby players often got away with pushing smaller boys around in the corridors - until they tried it on with the much more introverted boat-club rowers who (being much more highly weight and fitness trained) made them very sorry for it. ;-D
The swimming-pool inspection story sounds like a gross fabrication to me - but I do know that it was held important to not wear anyone else's shorts or trunks to avoid possibilities of cross-infections.
The only single instance I can think of in my 8 years at both schools that could possibly be (malignly?) construed as interference was at age 11 at Colet Court when the whole school year had an official medical inspection by an external doctor, with the school matron and nurse in attendance. After the weight/height/eyesight check, the ear and throat inspection and full breathing check with a stethoscope, we finally had to drop our shorts, the doctor gently supported the testicles with a couple of fingers and told us to cough as hard as we could, then pull our shorts up again, it was all over in about 5 seconds. Anyone medically trained care to clarify?