On 18 February 1949, police arrested a slim, well-dressed man named John George Haigh in a Kensington hotel after he confessed to dissolving human bodies in sulphuric acid. By the time he stood trial that July, the 40-year-old had become known as the Acid Bath Murderer, a figure so shocking that his name would echo through the history of British crime. Haigh claimed he had killed nine people, though he was eventually convicted of murdering only six. What made his crimes especially twisted was not just the method of disposal, but his calculated scheme to profit from each death: he would forge his victims' signatures, steal their possessions, and pocket thousands of pounds by impersonating them or selling their property.

Haigh's criminal mind developed early. Born on 24 July 1909, he grew up in a strict religious household and showed signs of deception and manipulation from childhood. As a teenager, he was already forging cheques and running small cons. By his early twenties, he had served time in prison for fraud. But it was in the 1940s, after World War II, that his crimes escalated from theft to murder. Between 1944 and 1949, he carefully selected victims who were either wealthy, isolated, or unlikely to be immediately missed. His targets included a wealthy widower, a retired surgeon, a landlady, and a husband-and-wife team of engineers. Haigh would gain their trust, invite them to his workshop in Crawley, West Sussex, and then kill them.

Haigh's method was grimly efficient. He would either bludgeon his victims with a hammer or shoot them, then drag their bodies to a large steel drum filled with sulphuric acid. The acid would dissolve flesh, organs, and bone within days, leaving only a greasy sludge that Haigh would dispose of down the drain or bury in the garden. He believed, wrongly, that the acid would completely erase all evidence of the crime. After each murder, he would forge documents in his victims' names, write letters claiming they had gone away, and systematically sell or transfer their assets. One of his victims, Olive Durand-Deacon, was a wealthy widow whose disappearance finally caught the attention of police. Her friend mentioned her missing diamond ring to investigators, and when police searched Haigh's workshop, they found human remains that dental records confirmed belonged to Durand-Deacon.

Once arrested, Haigh confessed with disturbing casualness, apparently believing his confession of even greater crimes would somehow impress the authorities or prove his superiority. He boasted about dissolving nine victims, yet only six murders could be proven with sufficient evidence. His trial in July 1949 was a sensation in British newspapers. Haigh's lawyers attempted an insanity defense, arguing that his gruesome crimes reflected a deeply disturbed mind, but the prosecution presented a cold portrait of a calculating man who understood the consequences of his actions and killed for greed. The jury deliberated for just 15 minutes before finding him guilty of murder.

On 10 August 1949, John Haigh was executed by hanging at Wandsworth Prison in London. His case became a watershed moment in British true crime, captured decades later in the 1962 television film A Is for Acid. Beyond the headlines and gruesome details, Haigh's crimes revealed how a seemingly respectable, articulate man could hide murderous intentions behind a veneer of charm and sophistication. He had worked as a draftsman and engineer, moved in middle-class circles, and lived in hotels and lodgings where no one suspected him of anything worse than petty fraud. His case taught investigators and the public that evil did not always announce itself loudly, and that careful, methodical planning could conceal horrific crimes for years. Haigh left behind a legacy that influenced how police investigate financial crimes connected to missing persons cases.