Young was released from Broadmoor in 1971, after eight years' detention. He initially stayed with his sister and her husband in
Hemel Hempstead. Within weeks he had resumed his interest in poisons, but an attempt to acquire poison from
John Bell & Croyden in
Wigmore Street was unsuccessful, as the chemist refused to sell them without written authorization. Young duly returned with the required authorization on
Bedford College headed notepaper and was sold 25 g of
antimony potassium tartrate. He told the chemist that he needed it for a qualitative and quantitative analysis. Young later returned to the same chemist to purchase 25 g of thallium.
Poisoning of Trevor Sparkes Young attended a storekeeping training course in
Slough and stayed at a
hostel in nearby
Cippenham. He befriended 34-year-old Trevor Sparkes, another resident of the hostel, and the two occasionally visited a
pub together or shared a bottle of wine in Sparkes' room. Young would later confess to poisoning Sparkes with antimony sodium tartrate. On the night of February 10, Sparkes fell violently ill, exhibiting diarrhoea,
pins and needles in his legs and pains in his testicles; earlier in the evening he had accepted a glass of water from Young. Sparkes' symptoms returned periodically over the following months. He felt so ill during a football match that he had to leave the pitch after a few minutes. Specialists were unable to pinpoint the cause, variously diagnosing it as a kidney infection, bowel infection,
urinary tract infection or stomach infection. Sparkes left Slough in April 1971 and gradually recovered.
Bovingdon Young secured a job as assistant storekeeper at John Hadland Laboratories in
Bovingdon,
Hertfordshire, near his sister's home in Hemel Hempstead. The company manufactured
thallium bromide-iodide infrared lenses, which were used in military equipment. However, no thallium was stored on site, necessitating Young obtaining his supplies of the poison from a
London chemist. On his application, Young falsely claimed that his lack of employment history was because he had suffered a
nervous breakdown following the death of his mother in a car accident. His employers received references as part of his
rehabilitation from Broadmoor, but were not informed that he was a convicted poisoner and a former Broadmoor patient. Young left Slough and rented a room in Maynard Road, Hemel Hempstead, at £4 per week. Young's new colleagues found him unpredictable; he could be surly and keep to himself, but on other days he could be more cheerful. During breaks, he usually sat alone reading, invariably a book on one of his favourite subjects: war, chemistry, the Nazis or famous murderers. Young was not talkative unless one of his favourite topics was being discussed. His duties at Hadland included collecting drinks from the tea trolley in the corridor and bringing them to the storeroom. Each employee had their own mug, which made it easier for him to target specific individuals for poisoning. Soon after Young's arrival at Hadland, he poisoned some of his co-workers, focusing on his immediate colleagues in the storerooms. His
modus operandi was to slip poison, usually antimony or thallium, into their tea or coffee. Victims would fall ill with symptoms that included vomiting, stomach pains, nausea and diarrhea. Initially, the mysterious illness was assumed to be a virus and was nicknamed the "Bovingdon Bug."
Poisoning of Ron Hewitt and Diana Smart During Egle's absences, Young targeted his assistant Ron Hewitt, poisoning his tea with antimony. Hewitt had already accepted a job at another company and was working his notice (Young was specifically hired as his replacement). After leaving the company, he suffered no further symptoms. As a result of Egle's death and Hewitt's departure, Young was promoted to head storeman for a probationary period. For the next few months, his poisonings were limited to small doses of antimony in his co-worker Diana Smart's tea, usually when she annoyed him. Young wrote in his diary: "Di [Diana Smart] irritated me yesterday so I packed her off home with an attack of sickness. I only gave her something to shake her up. I now regret that I didn't give her a larger dose, capable of laying her up for a few days."
Poisoning of David Tilson and Jethro Batt On 8 October 1971, Young put
thallium acetate in David Tilson's tea. Tilson found the tea too sweet for his liking (Young had added sugar to disguise any unusual taste from the thallium) and therefore did not drink it all. Young administered a second dose of thallium a week later. Tilson was admitted to hospital with numb legs, breathing difficulties and chest pains. His skin was so tender he could not endure the weight of the bedsheets, and all his hair fell out. Young had a back-up plan to visit Tilson in hospital and offer him a bottle of
brandy laced with more thallium. Subsequently, Tilson recovered, though he was left permanently
impotent by the poisoning. At the same time he was poisoning Tilson, Young also poisoned another Hadland employee, Jethro Batt. Batt had become friendly with Young and would give him a ride home to Hemel Hempstead. Young admitted to administering 4 g of thallium to Batt in two doses, enough to kill him. However, Batt found the coffee Young had made for him too strong and did not drink it all. Nevertheless, Batt was admitted to hospital with stomach and chest pains, and his hair fell out; the poisoning made him suicidal. Batt ultimately recovered, but like Tilson he was also left impotent. Young apparently felt some remorse for poisoning Batt, writing in his diary: "I feel rather ashamed in my action in harming J [Batt]."
Murder of Fred Biggs Fred Biggs, a 56-year-old local
councillor and part-time employee at Hadland, was poisoned by Young with antimony, prompting the typical "Bovingdon Bug" symptoms. Then, on 30 October 1971, Young put three doses of thallium acetate in Biggs' tea. By the following day, Biggs had developed chest pains and had trouble walking. Within days, he was admitted to Hemel Hempstead General Hospital, then transferred to the
Whittington Hospital in
North London, followed by the London National Hospital for Nervous Diseases (now part of the
National Hospital for Neurology and Neurosurgery). His
central nervous system deteriorated to the point that he could not speak and had trouble breathing, and parts of his skin peeled off. Young expressed concern for Biggs' condition, continually telephoning his wife and the hospital directly to make enquiries. Biggs finally died on 19 November 1971. ==Investigation and arrest==