A child of 14 is forced to walk on to a stage and strip to her underwear. Tiny and mute beneath the stacked rows of medical students, she is paraded for their benefit by a consultant psychiatrist some 44 years her senior. It is 1966 – the peak of Swinging 60s’ hedonism, liberalism and youthful counterculture – but in a locked psychiatric ward in London’s Royal Waterloo hospital, unspeakable violations are being inflicted upon patients.

The perpetrator-in-chief, William Sargant, is the subject of thriller writer Jon Stock’s first nonfiction book, The Sleep Room: A Very British Medical Scandal. One of the most notorious figures in British psychiatry, Sargant initially wished to be a physician. He pivoted to psychiatry after one of his earliest pieces of research met with a humiliating reception at the Royal College of Physicians, causing him to suffer a nervous breakdown and spend time in a psychiatric hospital himself. At this time – the 1930s – effective psychiatric treatments were virtually non-existent. Serious mental illness usually led to lifelong incarceration in an asylum. But the therapeutic nihilism of psychiatry was shifting towards optimism. Psychiatrists began experimenting with so-called “heroic” therapies, such as putting patients into insulin comas or giving them electroconvulsive therapy (ECT) to try to “reset” their brains.

Sargant firmly believed that a broken brain was no different to any other damaged organ or limb, and best fixed with aggressive physical treatment. Not for him the namby-pamby chitchat of Freud’s “sofa merchants” and their spurious talking cures. Rather, psychiatric illnesses such as depression, anxiety and schizophrenia could all be cured with excessive doses of drugs and electricity, or, if they failed, with surgical lobotomy. Sargant’s patients were sequestered away behind locked doors on the top floor of the hospital. The most infamous part of his ward was a six-bedded area known as the Sleep Room. Here, the patients, nearly all of whom were female, were drugged into long-term stupors, being roused from their beds only to be fed, washed or given innumerable doses of ECT. A typical “narcosis” treatment comprised three months of near-total unconsciousness, after which time the patient had often been reduced to a “walking zombie” with permanent memory loss.

The Sleep Room is peppered with haunting first-hand accounts of horrific treatment at the hands of William Sargant. The actor Celia Imrie, for example, the aforementioned child, was admitted under Sargant’s care because she was close to death from anorexia nervosa. She recounts being forced to drink such large doses of chlorpromazine – the first antipsychotic - that she dribbled, shook uncontrollably and found her hair in clumps on her pillow. She was injected daily with enough insulin to make her drowsy, weak, sweaty and near comatose. She remembers other women around her having huge rubber plugs jammed between their teeth before the high-voltage electricity of ECT was sent through their temples, and their bodies “shuddered and jerked” with the “scent of burning hair and flesh”. Sometimes a patient would reappear on the ward with their head thickly bandaged, scarcely able to walk after being lobotomised. Amid the moans, screams and stale stench of sleep, Imrie recalls the nurses reporting her own resistance to the drugs to Sargant, to which he ominously responded: “every dog has his breaking point”.

To say that these stories are difficult to read is an understatement. Even as someone who learned, as a medical student, about the unspeakable mid-century vogue for lobotomy – permanently subduing patients by gouging out parts of their frontal lobes – some of the accounts made my skin crawl. It is to Stock’s great credit that he places patient testimony centre stage, allowing several patients to tell their stories at length in their own, unedited words.

Sargant himself is depicted as a sinister, all-powerful, “simian” monster who ran his ward as a personal fiefdom in which he could pursue, unchecked, his conviction that effective treatments worked by physically erasing and reprogramming disturbed minds. A darker benefit of his Sleep Room was the absolute power it gave him over his charges. Once rendered unconscious, a patient could be subjected to treatments they might otherwise never have consented to, such as scores, or even hundreds, of doses of ECT. As Sargant himself put it: “What is so valuable is that they generally have no memory about the actual length of the treatment or the number of ECT used.” Before long, colleagues had nicknamed him “Bill the Brain Slicer” and “Sargant the Shock”. His fascination with techniques for brainwashing led to speculation that he may have collaborated with the CIA’s MKUltra programme into mind control, though no definitive proof of this is provided by Stock.

At least five of Sargant’s patients died during narcosis. The dangers of artificially prolonged sleep included deep vein thrombosis, pressure sores, infection and paralysis of the gut, all of which could be fatal. Though the disproportionate number of female patients under his care was not, in itself, evidence of misogyny, his treatment of particular individuals locates him firmly within that psychiatric tradition. He was perfectly willing, for example, to regard female independence as synonymous with madness and in need of social correction. One young woman was dispatched to Sargant by her wealthy businessman father after she fell in love with an “unsuitable” man in the 1960s. Sargant “helped” the situation by subjecting her to months of narcosis, ECT, antipsychotics, antidepressants and the “truth drug”, sodium amytal, after which she was successfully returned to her family with all memories of her boyfriend completely erased. Obedience had been achieved through physical obliteration of the mind.

While there is no denying Sargant’s lack of medical ethics, and his authoritarianism and reliance on dogma as opposed to clinical evidence, The Sleep Room can present him as almost cartoonishly villainous. With eyes “like washed black pebbles”, “sadomasochistic stubbornness” and a “prodigious enthusiasm for pill popping”, he sweeps the wards like a demented demigod, barking orders to terrified staff and patients alike. This portrayal unhelpfully flattens very real and complicated issues over how best to treat serious mental illness. Patient consent – the bedrock of all good medical practice – cannot always be obtained when a patient’s illness means they lack capacity to make decisions for themselves. Even today, with a modern emphasis on the rights of patients, the responsibilities of clinicians and the need for humanity in psychiatry, enforced treatment is sometimes the only way to prevent a severely unwell psychiatric patient harming or killing themselves. ECT, for example, although used much less frequently than in Sargant’s day (and rightly so), can be a life-saving last resort, as in patients with catatonic depression. With more nuance and less condemnation, Stock could have interrogated more richly the complexities of how best to treat disabling and life-threatening psychiatric illness.

Rachel Clarke’s most recent book, The Story of a Heart (Abacus), has been shortlisted for the Women’s prize for nonfiction 2025

• The Sleep Room: A Very British Medical Scandal by Jon Stock is published by the Bridge Street Press (£25). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply