Ronald Maddison: Sarin B was dripped onto his arm

Mr Maddison, from Swindon in Wiltshire, believed he had been taking part in experiments to find a cure for the common cold.

It is claimed he died after 200mg of the deadly nerve agent Sarin, was dripped onto a patch of uniform taped to his arm.

An inquest into his death was held in private for reasons of "national security".

The hearing in Salisbury returned a verdict of death from asphyxia.

But in 1999 another ex-serviceman, Gordon Bell, revealed what he claimed was the true cause of death.

Records of a board of inquiry held by top service chiefs inside Porton Down showed that Mr Maddison actually died from the deadly nerve agent.

Operation Antler

Mr Bell said: "This will open a can of worms, It will expose the lies told at the inquest and the false evidence put forward.

"To have an inquest in secret is completely undemocratic."

The coroner Mr Masters must now apply to the High Court asking it to quash the original verdict and open a new inquest.

The development comes three years after the BBC revealed that Wiltshire police were beginning an investigation into the deaths of more than 70 Porton Down volunteers.

As a result of Operation Antler files have been sent to the Crown Prosecution Service.

The Director of Public Prosecutions, David Culvert QC, will make the decision as to whether anyone will face criminal charges.

A spokeswoman for the Attorney General's office said the inquest was to be reopened on grounds of new information not available to the coroner in 1953.