Ddaullt station marks the start of the Llyn Ystradau Deviation on the 2' gauge Festiniog Railway in North Wales, and represents one of the major achievements of the British steam railway preservation movement.

In 1956, the 1842 route of the Festiniog Railway was flooded in the Ystradau Valley above Moelwyn Tunnel as part of the CEGB's Tanygrisau Pumped Storage Scheme. The FR, then being revived with the help of the Festiniog Railway Society, proposed to rebuild the line to Blaenau Ffestiniog bypassing the new lake and power station to the North. To gain height, a spiral formation unique to Britain, was constructed solely by volunteer labour, around Dduallt station.

The Deviation project was started in 1965 - the commemorative stone can be seen beside the line at the front of the layout - and the railway was reconnected with Tanygrisau once again in 1978. The abandoned 1842 route continued straight ahead from the station behind the signal box, seen on the right hand side of the layout.

The layout represents Dduallt station as many enthusiasts prefer to remember it, with its passing loop and associated paraphernalia in operation. The nominal date is 1988 - the year of the Steam 125 celebrations, for which all the FR's mainline steam locomotives were in traffic and the year when the carriage liveries were being changed from all over cherry to the two-tone "Mountain Prince" livery. Other more modern stock from the 1990's appears on the layout bringing the FR story up to date.

All the locomotives are constructed from brass or whitemetal kits, many with body and chassis adaptations to enhance their accuracy. Some of the coaches are also from commercially available kits, but the vast majority - and all the revival corridor vehicles - have been scratchbuilt.