Prof John Henry:Prof John Henry, who has died aged 68, was an internationally-renowned authority on drugs and poisons. Frequent television and radio appearances made him Britain's best-known toxicologist, and following his retirement in 2004 his expertise remained much in demand.
When Ukrainian opposition leader Viktor Yushchenko, fell mysteriously ill during the 2004 election campaign, Henry was sent a photograph of the patient, and straight away concluded that he had been poisoned by dioxin. A month later Yushchenko's doctors in Vienna confirmed the diagnosis.
His advice was also sought in the cases of the former KGB agent-turned-dissident Alexander Litvinenko and, most recently, Pakistan's cricket coach Bob Woolmer.
He had strong Irish links. His Mayo-born father studied at University College Dublin with Kevin Barry. His grandfather, Mark C Henry, was a member of Dáil Éireann. In later life he maintained a close association with the National Poisons Information Centre, based at Beaumont Hospital.
Dr Joe Treacy, the centre's director, this week said: "John Henry was a great friend of the National Poisons Information Centre and was always available when invited to come and lecture in Dublin. Always good company, he was a great raconteur and proud of his Irish origins. We will miss him."
Born at Greenwich on March 11th, 1939, he was the eldest of the four surviving children of John Aloysius Henry and his wife Emma Elphick. His father, a GP and keen sportsman, was team doctor to Millwall Football Club, and John acquired a lifelong interest in football. Educated by the De La Salle Brothers at St Joseph's Academy, Blackheath, he went on to study medicine at King's College, London. As a 20-year-old medical student, he joined Opus Dei as a "numerary member", pledging himself to a life of celibacy.
He attended Mass every day and made time twice daily for periods of prayer or meditation. His drive and devotion to his work, as well as his cheerfulness, stemmed from this deep spirituality.
On holiday in Italy in 1962 he caught a throat infection, which was incorrectly treated, leading to kidney failure, which was diagnosed some years later. Facing an uncertain future as a dialysis patient, he withdrew from medicine for five years.
He received a transplant at the Royal Free Hospital in 1976, the success of which he attributed to the intervention of St Josemaria, the founder of Opus Dei. Resuming his medical career he became a registrar at Guy's Hospital, where he was known for his deep empathy with the patients in his care.
In 1982 he was appointed consultant physician at the national poisons unit at Guy's. He saved many lives, particularly those of children who had accidentally consumed potentially lethal household products. He also held senior positions at a number of London's leading hospitals.
An excellent communicator, he happily cooperated with the media and was held in high regard by the many journalists he encountered over the years. His accessibility led on one occasion to his being tricked into appearing on Ali G's show, answering mischievous questions about class-A drugs.
He was very concerned about the damage caused to young people by illegal drugs. He rejected the notion that cannabis was harmless, insisting it was much more dangerous than tobacco, and was one of the first raise the alarm about the risks of taking ecstasy.
In 2003 he defused a scare about a planned ricin attack on the London Underground, pointing out that ricin would be fatal only if injected into the blood stream. He was chief medical editor of the BMA Guide to Medicines and Drugs.
His sisters Siobhán and Gabrielle and brother Michael survive him.
John Anthony Henry; born March 11th 1939; died May 8th 2007