53°11′06″N 3°11′20″W / 53.185°N 3.189°W The M.S. (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. It was later also used in the development of the UK's atomic bomb project. More recently, it became a bulk storage depot for emergency supplies.