The following obituary is from The Telegraph, Sunday 16 November, 2025

Tim Marrs in his student days: he later worked at Porton Down, the Department of Health and the Food Standards Agency - Courtesy of family

Timothy Marrs (SH 59-63), who has died aged 80, was a leading toxicologist who advised government and international agencies on everything from the classical poisons cyanide and arsenic, to chemical warfare agents such as the nerve agent Sarin, organophosphate insecticides and carcinogenic substances in food.

Much of his early research was undertaken at the Chemical Defence Establishment at Porton Down, where he worked from 1980 to 1990, becoming head of the pathology and clinical toxicology section. Stimulated by the reported use of chemical warfare agents in the war between Iraq and Iran and their use against Iraq’s Kurdish population, he had a special interest in the development of antidotes to these compounds and was a recognised authority in the field.

But his work was not limited to the use of chemicals in war. He was the co-author of a report into levels of cyanide found in the blood of victims of the devastating November 1987 fire at King’s Cross underground station. According to a later report in The Times, at least 23 of the 31 victims, including station officer Colin Townsley, the first fireman on the scene, were killed not by fire, but by cyanide released by a gloss paint applied to foil graffiti writers. The offending paint was subsequently removed from other escalator shafts on the Underground system.

Marrs co-wrote and co-edited several books, including Chemical Warfare Agents: Toxicology and Treatment (2007) and the multi-volume General and Applied Toxicology (1993), a key reference work, now in its third edition, covering the fundamental principles of toxicology and its practical applications.

Many of his research papers were published after his time at Porton but he maintained his interest in nerve agents. In 2018, following the assassination attempt on the Russian double agent Sergei Skripal, he co-wrote a paper entitled “Novichok: a murderous nerve agent attack in the UK”.

The younger of two sons, Timothy Clive Marrs was born in Edenbridge, Kent, on August 27 1945 to Wallace Myers and Barbara, née Hobson. From Tonbridge School he read medicine at Kings College London and qualified at Westminster Medical School.

Marrs: in retirement he ran a toxicology consultancy company - Courtesy of family

After a series of house jobs in and around London, the course of Marrs’s career became clearer with his appointment in 1970 as Senior House Officer in Clinical Pathology at Westminster Hospital. By the end of the decade he was senior lecturer and consultant at Westminster Medical School, in charge of the clinical chemistry and toxicology laboratories at St Stephen’s Hospital, Chelsea, and had been awarded his MD and MSc; he was later awarded a DSc by London University.

After his time at Porton, from 1990 to 2000 he was head of the pesticides and veterinary medicines section of the Department of Health. He moved to the Food Standards Agency when it was created in 2000 and served as chief toxicologist there until his official retirement in 2005.

For 20 years after his retirement he ran Edentox Associates, a toxicology consultancy company, and was consulting clinical toxicologist at the National Poisons Information Centre in Birmingham. He continued to publish and in 2022 was co-editor of The Coronavirus Pandemic and the Future: Volume Two, an account of the later stages of the pandemic, highlighting the consequent advances in science and vaccine development in order to place toxicologists and others involved in public health in a better position to advise in future epidemics.

Marrs, who was appointed OBE in 2004, was a convivial man who was unmarried but remained close to his older brother and his family. For 78 years, from the age of two, he lived in the family house in Edenbridge, which became a social hub for neighbours and his wider family, and friends from around the world. His annual garden parties were famous.