Tom Jones' diesel was a 4-6-4 diesel hydraulic locomotive partially built by Heathcotes of Cleator Moor in the 1950s. When the line closed and was then re-opened again, the construction was put on hold, however in 1969 the frames were sent away to Severn-Lamb of Stratford-on-Avon for completion. The chassis utilises parts from Ella, specifically the crankwebs and centre sliding axle. Originally the engine was a Ford 4D, as in Royal Anchor, and had a Linde hydrostatic transmission, however this was replaced in 1975 by a Perkins 6/354. In 1998 the engine was rebuilt into a diesel mechanical locomotive when she gained a Ford industrial engine with Spicer Compact Shuttle transmission. She is currently a mixed traffic engine and used throughout the year.