Shortly after 10am on this day 51 years ago, a young Royal Air Force serviceman walked into a sealed chamber wearing a gas mask and had 20 drops of clear liquid dripped onto a piece of cloth on his arm. After 23 minutes, he told those with him that he was feeling "pretty queer". Within half an hour, he was dead.
Yesterday, the final moments of Ronald Maddison, 20, were made public at the start of the first open inquiry into how Britain conducted secret experiments with the lethal nerve agent sarin on hundreds of personnel at the Ministry of Defence's most sensitive research complex, Porton Down in Wiltshire, during the early 1950s.
The fresh inquest into the death of the leading aircraftman, from County Durham, was ordered two years ago. His family and other veterans had won a High Court ruling that a verdict of misadventure reached in secret by an earlier inquest should be quashed after it was confirmed that the substance administered to LAC Maddison and five others with him had been 200mg of "pure" sarin.
Speaking before the inquest at Trowbridge, Wiltshire, the serviceman's sister, Lillias Craik, 70, said: "My brother was ... only 20 years old. My family has never been told why he had to die so young. We are grateful for the inquest so that we can finally know the truth."
A jury of six men and four women was told that LAC Maddison, who volunteered for the tests in return for extra pay and a weekend pass, had arrived at Porton Down, the MoD's chemical weapons experimentation establishment, as a fit ice hockey player on 2 May 1953.
The serviceman, based at RAF Ballykelly in Northern Ireland, was part of a constant flow of personnel passing through Porton Down after responding to notices at their bases asking for volunteers. Fellow veterans have said the notices claimed the tests were part of efforts to find a cure for the common cold.
Opening the inquest, the Wiltshire coroner, David Masters, said the nerve gas experiments were ordered at the beginning of the Cold War, when Britain and its allies were developing chemical weapons, many of them discovered in a Nazi laboratory, in the knowledge that the Soviet Union was doing the same. The hearing was told that on the day of LAC Maddison's arrival, scientists were conducting experiments to establish the lethal dose of sarin - known as LD50, the dose required to kill half a population of humans.
Mr Masters said the governments of the countries involved - Britain, Canada and the United States - were still sensitive about revealing details of their nerve gas programmes.
The coroner said that the Pentagon had retained five documents relating to the programme and that those papers, which it had reluctantly released, could only be discussed in closed session.
The Porton Down Veterans Association, many of whose members were at the hearing, is demanding an apology from the MoD and a full public inquiry. The inquest is expected to last for up to eight weeks.