There followed a decade of profitable years and Forest of Dean Stone Firms was taken over by United Stone Firms, a Bristol company, in 1909 who built up a fleet of their own steamers. Prospects were looking good but lying in wait for them around the corner was the First World War, virtually all their goods were despatched by sea and by the end of 1916 shipping was affected by the presence of German submarines in the Irish Sea and the Bristol Channel. The war period undoubtedly weakened the company, by the time hostilities ended the equipment was old and the company must have been short of cash. The railways would have been a much more efficient mode of transport but Porthgain was relatively remote and quarrying ended in 1931. At Abereiddi the quarry wall was blasted out to form a little harbour and is now romantically known as 'The Blue Lagoon' where the adventurous jump from heights into its depths. Porthgain meanwhile was under the ownership of a Sheffield company but also within the bounds of the Pembrokeshire National Park so quarrying was not deemed desireable, the National Trust bought the clifftop and the quarries and the villagers bought their houses from the company.
For the story in greater depth try 'Porthgain and Abereiddi' by Peter B S Davies available from Abe Books.