Complex sentence: The four locomotives supplied by England in 1863/64 to the Ffestiniog Railway were the first truly successful narrow gauge engines built and remarkably 4 survive, much rebuilt, two still in full working order.
Split into simpler sentences: The four locomotives supplied by England, in 1863/64, to the Ffestiniog Railway, were the first truly successful narrow gauge engines built. Remarkably four survive, much rebuilt, two still in full working order.