The ongoing inquest into the death of an airman who died in nerve gas tests in 1953 has been temporarily halted.
Mr Maddison was 20 when he died
The hearing into the death of Ronald Maddison, who died aged 20 after being exposed to sarin, was halted after the emergence of a new document.
David Masters, Wiltshire Coroner, sent the jury home so lawyers could discuss the impact of the document.
The material has been released by the MoD, but its contents could not be publicly revealed, the coroner ruled.
Submissions before the jury were expected to continue on Tuesday.
Leading Aircraftman Maddison, from County Durham, collapsed and died within minutes of having drops of sarin put on to his arm at Porton Down on Salisbury Plain.
He was one of many human volunteers involved in tests from 1939 to 1989, taking part in what he thought was an experiment to find a cure for the common cold.
The original inquest into Mr Maddison's death was held in secret for what were claimed to be "reasons of national security".
The inquest was expected to end in July and could now run until September.