An RAF man who died in secret nerve gas tests more that 50 years ago had been exposed to "uncontrollable danger", according to an unpublished report.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 into the death of airman Ronald Maddison in 1950s sarin experiments at Porton Down, near Salisbury, 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 Porton Down tests had been released by the Government.

He said that ethics expert 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. Mr Maddison, 20, died after being exposed to sarin on his skin during tests 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 of this year after campaigning by the Maddison family.

The hearing yesterday was told that 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 Professor Kennedy. And the coroner told the jury that Professor Kennedy had concluded that it had not been "safe" to proceed with the tests because of that fact.

The inquest continues