A number of the large industrial railways in the North East possessed the capacity to build complete locomotives and No.10 was the last example of new construction by such a railway for its own use. A 300 Horsepower locomotive with mechancial transmission was required at Consett in the mid 1950's but none was available; a design by the Hunslet Engine Co. of Leeds was therefore taken as a basis for the construction of two locomotives in the Company's shops at Templetown.

C I.C Locomotive Engineer, Mr George Cowell prepared the design and he directed construction during lulls in repair work; a number of components were re-used from steam locomotives and only the Power Unit and tyres were bought-in for the first example.

A Mirrlees J4 Diesel engine of 300h.p. is fitted to No.10 and the drive is taken through a conventional friction clutch to a four-speed gearbox. Final drive to the wheels is provided by fly-cranks and coupling rods.

The deep buffer beams which almost reach rail level are a common feature of steelworks designs and they prevent the locomotive dropping too far on to the ballast in the event of derailments. No.10 was used for the same heavy duties as the Company's steam locomotives of the long-boiler type and it remained in use until the British Steel Corporation replaced most of the diesel-mechanicals in the works by "Sentinel" locomotives with hydraulic transmission. The locomotive was presented to the Museum Service by the British Steel Corporation in 1976.