The 1ft 11½in gauge Welsh Highland Railway started life in 1877 as the North Wales Narrow Gauge Railway between Tryfan Junction, 3 miles south of Caernarfon on the LNWR’s Bangor-Afon Wen route, to Rhyd-ddu in Snowdonia, 9 miles away. It was never a financial success and closed throughout in 1916. The Colonel played a part in its revival and surveyed an extension through to Porthmadog, which opened throughout in 1923, by which time the 20-mile line had become the Welsh Highland Railway.
From this date, Stephens became the civil engineer and locomotive superintendent of both the Welsh Highland and Festiniog railways, which at this time were under joint management. He retained these positions until his death in 1931.
Since 1951, the Ffestiniog Railway has been running as a preserved steam railway. The Welsh Highland Railway Ltd has been running trains from Portmadog and planning the total reconstruction of the WHR. However, in 1999 the Ffestiniog Railway was given permission to start work began on reconstructing the WHR, which was closed in 1937 and dismantled in 1941. The first rebuilt section, the three miles between Dinas Junction and Waunfawr, opened in August 2000. The aim is to eventually reopen the entire route to Porthmadog. The FR has to include and work with the WHR in this project.