Leading Aircraftsman Ronald Maddison died at the base in 1953
The family of an RAF man who died after a nerve gas experiment at the Porton Down military research centre in Wiltshire in 1953 has won £100,000 in compensation from the Ministry of Defence, the BBC has learned.
This brings to an end a long and controversial campaign for justice following the death of 20-year-old Ronald Maddison, of County Durham, after the nerve agent Sarin was dropped onto his arm.
The move comes as lawyers representing 500 veterans of Porton Down say they are ready to launch a multiple-action law suit against the MoD to seek compensation for their injuries.
The payment for the Maddison family will be shared by eight surviving relations and one of his sisters, Lilias Craik, said she was pleased that the battle with the Ministry was now over.
Speaking exclusively to the BBC at her home near Mansfield in Nottinghamshire, she said: "It is a great relief. I am still angry at what happened, but I am pleased it is over. I can't forget what they did and I can't forgive them.
"The compensation will not make us rich but it does bring this to an end. They took his life and should be made to pay for it."
Mrs Craik said her campaign was less about the money and more about recognition for how her family had suffered.
In the wake of Ronald Maddison's death, few details were disclosed. At the time an inquest returned a verdict of accidental death and for half a century the case remained closed.
But when new evidence came to light, Wiltshire Police launched an investigation and eventually a second inquest was ordered. In 2004 a jury returned a verdict of unlawful killing.
Alan Care, a lawyer acting for the Maddison family, said he hoped the settlement would now pave the way for compensation and recognition for the 500 veterans who claim they suffered from the experiments.
"They've got nowhere else to go. They've been calling for a judicial enquiry and that's always been refused. Now they can only pursue their claims for personal injury."
One veteran, Ray Coughlin, told the BBC how he had collapsed after one experiment in a gas chamber at Porton Down in 1969.
"I was pouring sweat. My head was exploding. I was kept in hospital for two days in isolation," he said.
The trials of chemical weapons came during the height of the Cold War amid fears that the Soviet Union was deploying nerve agents.
Scientists at the time argued that the experiments were vital to help prepare for chemical warfare.
The MoD has issued a short statement, saying: "We very much regret the unfortunate death of Ronald Maddison. We are extremely pleased that an amicable settlement has been reached".
When asked about the multiple legal action for compensation, there was no comment.