As a student in the 1960s, Alastair Hay was involved in the anti-apartheid movement and protests against the Vietnam War. As a scientist, he felt he had more to offer than simply "picketing the US Embassy" and went on to devote much of his career to a crusade against chemical warfare.

This campaign, which has taken him to Vietnam, Bosnia and Iraq, culminated in an international treaty, now signed by 180 countries worldwide, banning chemical weapons.

His success, achieved alongside a career in academia, has been honoured by the University of Leeds as the institution's most significant contribution to "changing the world". Professor Hay, who joined Leeds in 1977 as a postdoctoral researcher, is still at the university, as a professor in the Molecular Epidemiology Unit, 30 years on.

His concerns about the use of chemical agents began with the war in Vietnam, where US forces used toxic herbicides to strip foliage during jungle warfare. They continued at the height of the Cold War, when both the Soviet and US governments built stockpiles of agents. "Chemical warfare looked a real threat. Both sides were bristling throughout the 1980s," Professor Hay said. "Part of the problem was that when statements were made by governments there was no one around to challenge them."

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He and fellow scientists launched a petition, signed by five Nobel laureates, which was followed by a book setting out their objections to chemical warfare.

One of the problems they faced was a clause in the Geneva Convention reserving the right of countries to respond "in kind" to any attack, chemical or otherwise. "We felt we needed something that was quite categorical, that would get rid of the stockpiles, subject countries to inspections and so on," he said.

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The treaty that resulted in 1993 has been signed by most of the world's nations, barring North Korea and a handful of countries in the Middle East. The process of destroying the huge stockpiles of chemical agents - Russia inherited 40,000 tonnes from the Soviet regime while the US had 30,000 tonnes - continues.

Professor Hay was a friend and colleague of David Kelly, the biological weapons expert who committed suicide after being named by the Government as the source of a BBC story about the so-called dodgy dossier that made the case for the Iraq War. He said Dr Kelly's expertise and tenacity had been feared by the Saddam regime, and that the Government had behaved "outrageously" in its treatment of him.

The treaty, he said, was holding firm and he hoped the restrictions it imposed would not hinder science, but allow chemists to channel efforts in a more positive direction.

john.gill@tsleducation.com.