Complex sentence: Road access to Plas Dduallt is recent and during the 1960's and 70's the Colonel kept his own locomotive on a siding by the halt and which he ran to and from Tan-y-Bwlch under an operating agreement with the Ffestiniog Railway.
Split into simpler sentences: Road access to Plas Dduallt is recent and during the 1960's the Colonel kept his own locomotive on a siding by the halt. He ran his own train to and from Tan-y-Bwlch under running powers granted by the Ffestiniog Railway.