This locomotive is Ruston & Hornsby Type 40DL 4wDM (Builder's number 297030 of 1952). It was supplied new for use at Blockley's Hadley Lodge Brickworks at Telford in Shropshire and was purchased by the WHLR (1964) Company and moved to the Kinnerley site in October 1964.
It was moved to the Llanberis Lake Railway in August 1976, where it was known as No.10 YR ENFYS and was used in 1978-9 for the power transmission cable laying project along the shores of Llyn Padarn. It arrived at Porthmadog ( WHR(P) ) on 1 June 1980.
The locomotive has been rebuilt with a large cab and has been fitted with a Perkins 6.354 diesel engine and an air compressor for passenger train use. It has proved to be very useful for passenger duties.
See The Welsh Highland site for more information