Before waterboarding, there was wall standing.
The Guineapigs is a book by John McGuffin. It was published in 1974, at the height of "The Troubles" in Northern Ireland, and banned in Britain almost immediately.
The "guineapigs" in question were 14 men from Northern Ireland detained by British security forces during the 1971 campaign of internment of suspected Irish Republican Army militants and sympathizers. The book details the treatment they experienced in the week after their detention, specifically "sensory deprivation".
The men were forced to stand up against a wall, with a black hood over their head, in a room into which a loud noise - described as something like a jet engine or gushing water - was played. If they fell or otherwise moved from this stance, they were forced back up. This went on for up to 48 hours, during which time they were given neither food nor sleep.
After this the treatment became a bit less harsh, and they were interrogated at various intervals. After about a week, they were released into a "normal" prison, and the story came out. A government inquiry, the Compton Report, followed, confirming that the "Questioning in Depth" had occurred but denying that it constituted "brutality".
The Guineapigs contains first person accounts from several of the men, describing the disorientation, hallucinations and terror they experienced during the procedure, and also details the psychological after-effects they reportedly suffered, including several cases of mental illness and at least psychiatric hospitalization.
McGuffin's most controversial claim was that the whole thing was a psychological experiment. It could not, he said, have been meant to gather useful information per se, because the 14 "subjects" were not especially high-value suspects; they seemed to have been chosen at random from the hundreds interned. Instead, he said, it was a research project, a trial of the technique of sensory deprivation as torture.
During the 1960s and 1970s there was lots of academic research on sensory deprivation, in which volunteers often reported hallucinations, paranoia, mood changes and other "psychotic" symptoms after being deprived of sight, sound and touch stimuli for a few hours. According to McGuffin, the British government decided to "field test" to procedure to see whether the same thing happened in "real life" with test subjects who weren't willing volunteers.
I'm not sure whether to believe this explanation of what happened; McGuffin was hardly an unbiased observer - he was himself interned in 1971, although he wasn't amongst the guineapigs - and he was a lifelong opponent of British rule in Northern Ireland. We'll probably never know for sure. But maybe it's as convincing as any other explanation.
Links: Lots of the book is online here. Mind Hacks on a recent sensory deprivation study, and a documentary about s.d. interrogation during WW2. I found a paper by T Shallice (1972) on The Ulster depth interrogation techniques and their relation to sensory deprivation research, but I haven't been able to access it yet. John McGuffin obits.