A special from Wolverhampton formed of Swindon Cross Country Class 120 DMU Nos W50652, W59260, W50701

Although a few diesel excursions had ventured into Mid Wales in the early 1950s, namely a GW single-car unit, DRC. No. 14 in 1953 on the occasion of the SLS rail tour to Welshpool and the WL&LR and the Talyllyn Railway Preservation Society excursions to Towyn in 1954, and the first BR DMU to visit the Cambrian on the 8th September 1957, when an eight-car excursion ran from Llandudno to Aberystwyth. However, the most significant event with regard to future diesel traction over the 'Cambrian' occurred in 1958 when a DMU Special Test Train ran across central Wales on Tuesday, 18th February. This three-car Cross Country set class 120 left Wolverhampton Cannock Road at 7.32 a.m. for Ruabon and Barmouth (arr 11.26 a.m.). It then worked from Barmouth, calling at all stations to Dovey Junction, before returning to Barmouth by 5.05 p.m.. After an overnight stop, it set out the following day (8.40 a.m.) again calling at all stations and halts to Pwllheli (arr 10.45 a.m.). Departure from Pwllheli was at 11.15 am when it travelled via Barmouth and Ruabon en route to Cannock Road. A week earlier, the same unit had worked from Cannock Road via Shrewsbury and Aberystwyth to Carmarthen, then after another night's stopover, returned to Cannock Road the following day, 12 February. The picture shows the unit at Barmouth on 18th February 1958. The rearmost vehicle isn't part of the train.