But until 1978, small amounts of nerve gas were made at Nancekuke in Cornwall, when it housed the Process Research Division of the Porton Down Chemical Defence Establishment, and Britain nearly rearmed with chemical weapons in 1963. Although the Nancekuke site was, like the one remaining site at Porton Down in Wiltshire, meant to help develop defences against chemical attack, some of the work done there was used by the United States to develop offensive chemical weapons as late as 1964. The chemicals made there included the nerve agents sarin and VX.
The 240-page report is Britain's declaration to the Organisation for the Prohibition of Chemical Weapons (OPCW) as now required by the international Chemical Weapons Convention (CWC), which came into force on 29 April, and to which Britain is a signatory.
Now, Britain maintains a "single small-scale facility" at Porton Down, run by the Defence Evaluation and Research Agency, which is allowed up to one ton of chemical agent to help develop defences under the treaty, although the Ministry of Defence said that a very small quantity was also kept at the Royal Military College of Science in Shrivenham, Oxfordshire.
The report reveals that more than 40,000 tons of chemical warfare agents - phosgene, mustard gas and tear gas- were manufactured during the Second World War, although none of the major combatants used chemical weapons in battle against another. After the war, captured German bombs containing nerve gas - a German invention - were brought to Britain, both for experimental use and as weapons. In 1956, the Cabinet decided to halt production of nerve gas and most of the chemical weapon stocks were destroyed.
In 1963, the Cabinet recommended that Britain reacquire offensive chemical weapons for retaliation in case the Soviet union and its allies used them, but, the report says, "for a variety of reasons including economic pressures and a political reluctance to rearm with these weapons, the recommendation was never implemented".
Britain tabled the first draft Chemical Weapons Treaty in 1976. It signed the current CWC on 13 January 1993, and ratified it a year ago. The convention obliges signatories to release details going back to 1946. It reveals that the British stocks, including half a million 25lb artillery shells filled with mustard gas and 58,000 phosgene and mustard gas 500lb bombs for the Royal Air Force, were largely obsolete, compared with the nerve agents the Germans had developed. Also kept in store were 71,000 German bombs filled with the nerve agent tabun, which were incompatible with RAF aircraft.
The report lists all the sites in Britain where chemical weapons were manufactured and stored. It also reveals there was a Chemical Defence Research Establishment in India, closed before the country's independence in 1947, and that hot-climate trials were carried out in Nigeria in the early Fifties, and in Malaya.
The Chemical Weapons Convention allows each signatory country a single, small-scale facility, which in Britain's case is Porton Down. It says that experiments must be carried out in small-reaction vessels which cannot operate continuously, and it limits their capacity. Britain's, the convention says, is 160 litres.