The manufacture of nerve gas at Nancekuke began in the 1950s

Nancekuke was a secret government base, which operated as a small-scale chemical production and research facility between 1951 and 1976.

In that time it manufactured about 20 tons of nerve gas, including Sarin.

The multi-million pound clean-up programme will take several years to complete.

The fact they were producing very dangerous chemicals here was upsetting Councillor Pat Aston

The site is now an RAF base, but for many years local residents, MPs, councillors and environmental campaigners have called for the area to be cleaned up.

Over the next four weeks, preliminary tests will be carried out at the smallest of the five dump sites, to establish what sort of chemical substances are present .

"I have to say the Environment Agency, Kerrier District Council, Cornwall County council and ourselves do not anticipate finding any chemical weapons or their breakdown products," said Wing Commander Peter Stokes, RAF Project Co-ordinator.

"But because the closure reports were incomplete we are not going to guarantee we are not going to find something and therefore we have to undertake this sampling regime and put in the high standards of safety."

The start of the work has been broadly welcomed by those who campaigned for it, but they warn that local people's fears will not fully be allayed until the clean-up is complete.

Seven-year process

"The fact they were producing very dangerous chemicals here was upsetting," said Councillor Pat Aston of Kerrier District Council.

"People resented it being done here as an experiment and they want it to be made better.

"They won't be happy with it until they know what was here, entirely, and that anything that was here is now gone."

The excavation of the first dump is due to start in spring 2005, and the clean-up of the final site is set to be complete in seven years time.