Cafodd y trenau poblogaidd Class 37 sy'n cael eu tynnu gan loco eu hychwanegu dros dro at y fflyd ym mis Mai 2019 i helpu i wella'r capasiti ar unwaith ar reilffordd brysur Cwm Rhymni - eto mewn ymateb i'r galw gan gwsmeriaid am seddau ychwanegol.
The popular class 37 loco-hauled trains were temporarily added to the fleet back in May 2019 to help provide an immediate capacity boost on the busy Rhymney Valley line – again in response to demands from customers for extra seats.