The Ministry of Defence is reopening a 30-year-old inquiry into a series of deaths and serious illnesses at a chemical weapons factory in Cornwall amid accusations that the original report was the subject of a high-level cover-up.
The MoD's decision follows a vigorous campaign by local activists to get the case looked at again and a series of articles in the Independent on Sunday which highlighted 41 deaths and a high incidence of serious illness among workers at Nancekuke, which produced deadly Sarin B nerve gas.
The MoD is also carrying out an environmental survey of the site after it admitted for the first time earlier this year that equipment used to manufacture Sarin B had been dumped in mine shafts and a quarry.
Nancekuke, near the holiday village of Portreath, served as a top-secret chemical research establishment for 20 years after the Second World War, supplying nerve gas to Porton Down. It was built using laboratory equipment recovered from Nazi Germany.
Since 1970, the MoD has maintained that Nancekuke poses no health threat. An official report 30 years ago into the deaths of the 41 workers claimed that was in line with the national average.
A second study, Sickness Experience at Nancekuke, which looked at medical records between 1959 and 1969, was suppressed. It showed staff at the plant were 33 per cent more likely to suffer from serious illness and 50 per cent more likely to suffer from respiratory diseases - a classic symptom of nerve gas exposure.
Now the MoD has promised to re-examine the evidence and the conclusions. The move follows a meeting between Candy Atherton, the Labour MP for Falmouth and Camborne, and the Defence minister, Baroness Symons of Vernham Dean.
Evidence that the conclusions in the 1970 sickness report had been manipulated by Whitehall came to light only at the turn of the year. It includes a draft of a 1972 letter, obtained by the Independent on Sunday, from the MoD to John Pardoe, the local MP at the time, which was significantly altered before it was sent.
Instead of reporting on "morbidity... a third higher over 10 years", the final version stated that the establishment had "experienced higher rates of absence than might have been expected ... but it would be unwise to draw any firm conclusions".
Ms Atherton, who has succeeded in reopening a case which has defeated previous local MPs, said: "They are looking at the 1970 report which declared Nancekuke safe. They will call in independent statisticians to review again the conclusions drawn by that report."
The new analysis could show that, for decades, civil servants fed false figures to ministers who then rehashed old answers to a succession of local MPs, she said. "The 41 deaths have always seemed a much higher than average death rate to me. I found it extraordinary the MoD has always alleged it isn't."
Ms Atherton will hand over her evidence of former workers who claim to have suffered from nerve gas poisoning.
One of them is Tom Griffiths, 79, who received £110 compensation in an out-of-court settlement in 1976, 18 years after being exposed to a nerve gas leak. The MoD admitted negligence in 1971.
Mr Griffiths, who maintains the leak left him with long-term heart problems, depression and impotence - for which the MoD denies any responsibility, said: "I have always thought the report was a whitewash but proving it was something else.
"Nancekuke has been kept under a cloak of secrecy but maybe now the truth will come out. The only problem is time is not on my side."
Campaigner Liz Sigmund, who helped to expose Nancekuke's secret role in the late 1960s, said: "I think there was a cover-up. A lot of weasel words were used at the time. The Government chose its statistics and facts carefully to cover up what really went on."
An independent survey of the site, now home to RAF Portreath, is currently being conducted and a report will be made to the MoD at the end of the month. It is promising a complete clean-up if evidence of lingering contamination is discovered.
A spokesman for the MoD said: "There are certain inconsistencies so we feel it's best to send the sickness report back to the statisticians."