Mining output and the ironfounding businesses in the Llynfi and Ogmore valleys continued to grow, and indeed it was obviously outstripping the limited capacity of Porthcawl harbour to handle it. Although the Llynvi Valley Railway was partly mixed gauge, the Ogmore Valley Railway was narrow (standard) gauge and the two railways were operated in close collaboration. The South Wales Railway had become part of the Great Western Railway in 1863. Use of that line to convey the mineral output away was of limited use because it was broad gauge only.