AN expert researching the death of a so-called human guinea pig during 1950s chemical warfare tests has claimed he found no evidence linking the experiments with research into a cure for the common cold.

At the reopened inquest into the death of North-East airman Ronald Maddison, historian John Harding spoke of what he had found in an extensive search of Government archives as part of a police investigation into the cases of hundreds of servicemen who took part in tests at the site.

Mr Maddison's family, who spent years campaigning for the inquest into his death to be reopened after the original hearing was held behind closed doors, believe he was tricked into taking part in the experiments as part of a quest to find a cure for the cold.

The 20-year-old airman, from Consett, County Durham, was exposed to 200mg of the nerve agent Sarin at the Ministry of Defence's Porton Down research facility, 51 years ago, and died within an hour.

During questioning from Wiltshire coroner David Masters, Mr Harding, who recently retired as a Ministry of Defence civil servant, told the court he searched for documents linking Porton Down with a volunteer programme to research a cure for the common cold, but found nothing in that category.

He said: "There was clearly Service involvement in the influenza trials, but that appears to have been separate to Porton Down.

"There were cases when Service bases were visited to vaccinate Servicemen."

Mr Maddison's original inquest, which recorded a verdict of death by misadventure, was held in private in the interest of national security on the order of then Home Secretary Sir David Maxwell-Fyfe.

Following years of campaigning by Mr Maddison's relatives and other veterans, Lord Chief Justice Woolf ordered the inquest be reopened and lawyers have warned that it is a benchmark case that could lead to a civil action against the Government.

The inquest was adjourned until Monday.