Moelwyn Tunnel, 686m long, was completed in 1842 and replaced the original inclines of 1836, thus allowing the Ffestiniog Railway (nprn 34660) to have a continuous gradient from end to end. It was cut in the 1950s by the British Electricity Authority during construction of a reservoir and hydroelectric power station near Tanygrisiau (nprn 401209), sealed up and abandoned. A new tunnel (nprn 407723) was excavated to the west to carry the re-aligned railway between Dduallt (nprn 309125) and Tanygrisiau stations.
B.A.Malaws, RCAHMW, 22 May 2008.