During the 1930’s and the threat of war with Germany looming the government decided a facility capable of producing and storing chemical weapons was required. In 1939 after surveying many sites in the area work was started in Rhydymwyn building one of the UK’s top and best kept secrets, which remained so until it’s cover was blown by media interest in the 90’s. The site was soon up and running even though construction was not complete. Several different weapons were made here but Mustard Gas was the main product, and this was made in two forms Pyro, which was the same as the gas used in the First World War, and Runcol, which was developed later. Pyro had a major disadvantage compared to Runcol as it could not be used at altitude due to it’s high freezing point, so it could not be dropped form the air and was the preferred method of delivery.
Runcol became the main product to be produced and this soon became a problem with tunnelling of an under ground storage facility not complete two above ground sites were chosen for temporary storage.
During 1942 Pyro production was at a stand still but remained ready to start up if chemical weapons were ever used against us and so one of the pyro buildings (P6), became the home of an Ultra Secret Project known as Project X and becoming an Atomic Research Facility. By 1943 there was large-scale uranium separation and research into Isotope separation. This was some of the earliest work to be carried out on the development of the Atomic Bomb and continued until the Americans joined the war; research was then transferred out of Valley and became the Manhattan Project. After the war chemical production was halted and Britain now had a new problem. We now had huge stockpile of Chemical Weapons and so did Germany. The government decided that Germany’s weapons would be safer over here out of harms way where they couldn’t fall into the wrong hands. It’s not clear how but they were brought over here and ended up being stored at Valley. They were later processed and graded on site. Depending on the grading it was either burnt or buried in pits of bleach on site. The rest was moved out and put onto ships which where scuttled in the Irish Sea, this was known as operation Sand Castle. As the site was wound down it was still being maintained and Chemical Weapon production capability remained well into the 50’s. Modifications where carried out on site this included reinforcing of the tunnel entrances and the fitting of blast doors. Valley remained in a shroud of mystery, as it became a Forward Supply Depot in the Cold War. There were secret plans for the tunnels, which were Projects Wellbright, Mallard and Trojan. Project Wellbright was the plan to locate the NATO Oil Executive Board (NOEB) at Valley, Project Mallard the storing of the Bank of England gold and Project Trojan the utilisation of the tunnels as a safe haven in the case of nuclear attack. The locals didn’t know much about the place. It was know as ICI or the rubber factory. Back in it’s early days it was also known as a Synthetic Rubber factory to help hide it’s real purpose. By this time it was the UK’s premier Nuclear Bunker, a bit ironic really being where the Atom bombs development was started.