AN airman from the North-East who died in secret nerve gas tests more that 50 years ago had been exposed to "uncontrollable danger", according to an unpublished report, an inquest heard yesterday.

The hearing into the death of Ronald Maddison in 1950s sarin experiments at the Ministry of Defence's base at Porton Down, Wiltshire, was told that a leading ethics expert had raised serious questions over the safety of the trials.

Reopening the long-running inquest after a summer break, the coroner for Wiltshire and Swindon David Masters told the jury that the final chapter of a key report on the tests had been released by the Government.

He said that Professor Sir Ian Kennedy had concluded that scientists at the time had been aware of the importance of the level of fat in volunteers' skin.

The 20-year-old Leading Aircraftsmen from Consett, County Durham, died after being exposed to sarin on his skin in 1953.

The original inquest shortly after his death had been held behind closed doors for reasons of "national security" but was finally reopened in May this year after campaigning by the Maddison family.

Lawyers say that the outcome could lead to legal action by Porton Down veterans who claim they were duped into taking part in dangerous trials.

The hearing yesterday was told that Mr Maddison's skin had a lower than average level of surface fat, which could have affected the way in which the sarin was distributed.

But there was no procedure available at the time for measuring how much fat the volunteers had in their skin, according to Prof Kennedy.

And the coroner told the jury yesterday that Prof Kennedy had concluded that it had not been safe to proceed with the tests because of that fact.

The coroner told the jury that they would have the chance to hear from Professor Kennedy in person later in the inquest.

But summing up some of Prof Kennedy's conclusions, the coroner said the professor felt the volunteers, including Ronald Maddison, were exposed to "uncontrollable danger of serious harm or death and therefore, on this assumption that it was not safe to proceed with this and allied experiments or trials".

The jury heard that because of Prof Kennedy's report, the coroner had decided to recall two previous expert witnesses to assess the controversial conclusion.

The inquest, which is likely to be seen as a test case, was adjourned until today.