M. S. Factory, Valley

(Ministry of Supply) Factory, Valley was a Second World War site in Rhydymwyn, Flintshire, Wales, that was used for the storage and production of mustard gas.

However, in 1939 the land was purchased by the Ministry of Supply and developed as a purpose built chemical weapons factory and storage facility.

Over 100 specialised buildings were constructed across the site, linked by an extensive rail network established around a spur off the Chester to Denbigh mainline.

Other major landscaping undertaken at this time included the canalisation and culverting of the River Alyn, and the excavation of a complex of interlinked subterranean, rock-cut tunnels and caverns.

During World War II the plant produced ordnance containing mustard gas, and was associated with the development of the Atom Bomb.

From the mid-1960s the site was used by various governmental departments, its major function being a buffer storage depot to supply emergency rations and foodstuffs, and associated facilities such as mobile bakeries and canteens.

[1] In the late 1930s the Chamberlain Government planned that the United Kingdom should be in a position at the beginning of any war to retaliate in kind if the Germans, as expected, used mustard gas.

[1] On accepting the findings of the Maud Report in 1941, the government of the day needed to verify that a cost-effective atomic bomb could be manufactured.

This required verification that a gaseous diffusion process would work on an industrial scale to provide enough fissile material to manufacture a cost-effective and timely atomic bomb.

Four prototype gaseous diffusion plants were ordered from Metropolitan-Vickers, at Trafford Park, Manchester, at a cost of £150,000 and installed in the P6 building at Valley.

The western side of the site is semi-ancient deciduous woodland with an understorey of wild garlic, snowdrops, bluebells and orchids.