the rail heads) was the important one. A standard gauge for horse railways never existed, but rough groupings were used; in the north of England none was less than . Wylam colliery's system, built before 1763, was , as was John Blenkinsop's Middleton Railway; the old plateway was relaid to so that Blenkinsop's engine could be used. Others were (in Beamish) or (in Bigges Main (in Wallsend), Kenton, and Coxlodge). English railway pioneer George Stephenson spent much of his early engineering career working for the coal mines of County Durham. He favoured () for wagonways in Northumberland and Durham, and used it on his Killingworth line. The Hetton and Springwell wagonways also used this gauge. Stephenson's Stockton and Darlington railway (S&DR) was built primarily to transport coal from mines near Shildon to the port at Stockton-on-Tees. Opening in 1825, the initial gauge of was set to accommodate the existing gauge of hundreds of horse-drawn chaldron wagons that were already in use on the wagonways in the mines. The railway used this gauge for 15 years before a change was made, debuting around 1850, to the gauge. The historic Mount Washington Cog Railway, the world's first mountain-climbing rack railway, is still in operation in the 21st century, and has used the earlier gauge since its inauguration in 1868. George Stephenson used the gauge (including a belated extra of free movement to reduce binding on curves) for the Liverpool and Manchester Railway, authorised in 1826 and opened 30 September 1830. The success of this project led to Stephenson and his son Robert being employed to engineer several other larger railway projects. Thus the gauge became widespread and dominant in Britain. Robert was reported to have said that if he had had a second chance to choose a standard gauge, he would have chosen one wider than . "I would take a few inches more, but a very few". During the "gauge war" with the Great Western Railway, standard gauge was called "narrow gauge", in contrast to the Great Western's broad gauge. The modern use of the term "narrow gauge" for gauges less than standard did not arise for many years, until the first such locomotive-hauled passenger railway, the Ffestiniog Railway was built. Adoption In 1845, in the United Kingdom of Great Britain and Ireland, a Royal Commission on Railway Gauges reported in favour of a standard gauge. The subsequent Gauge Act ruled