Mr Maddison died at Porton Down in 1953

Friends and relatives of an RAF man, killed in nerve agent trials, held a two minutes' silence during an inquest.

The inquiry into the death of Ronald Maddison, 20, was adjourned as a mark of respect, 51 years to the day after the incident.

The investigation is examining events surrounding the Porton Down tests.

Mr Maddison's sister Lillias Craik, 70, was among those who gathered at Thursday's Trowbridge hearing.

Mr Maddison became ill after being exposed to a few drops of the nerve agent Sarin in May 1953. Within an hour of the test, he was dead.

I would like to know a bit more about my son's death as I am not satisfied John Maddison

Mr Maddison had volunteered to go to the biological and chemical weapons research base on Salisbury Plain, Wiltshire.

The original inquest recorded a verdict of death by misadventure.

But, after years of campaigning by his family in County Durham, the report into how and why he died is being re-examined.

Wiltshire coroner David Masters told how the RAF man's father had visited the base to be told how his son died after taking part in the tests with five others.

Common cold

Military documents claim Mr Maddison Senior was satisfied with what he was told.

John Maddison agreed to protect "national security" by simply telling the family his son had died from "an unfortunate accident while on duty".

But a letter written to the military bosses from Mr Maddison revealed he rejected an offer of �3 towards funeral expenses, saying: "I would like to know a bit more about my son's death as I am not satisfied with what I have been told."

The family claims Ronald Maddison was tricked into taking part in the experiments in the belief it was a quest to find a cure for the common cold.

Last year the police and Crown Prosecution Service announced no criminal charges would be brought against those responsible for the experiments.