This locomotive, a Motor Rail 20/28hp 4wDM (Builder's number 8703 of 1941) was one of many of this type built during World War II. It was initially used on wartime construction projects by Sir Alfred McAlpine and Co.
Later in the ownership of the Yorkshire, Ouse and Hull River Authority (subsequently the Yorshire Water Authority), it was used on temporary railways on river bank works.
In December 1980, it was purchased from the YWA's Riccall Depot and arrived in Porthmadog, Welsh Highland Railway Ltd, on 27 February 1981, proving very useful for shunting and maintenance duties. After the arrival of the electric starting Model 60s locos, it rapidly fell out of regular use by the engineering department; however it is frequently to be seen at galas and on ocasional works duties.
It retains the Yorkshire Water two tone blue paint in preservation, and is a valuable asset to the shed tour.
See the WHRL site for more information.