This delightful award-winning 3 1/2in. gauge model of an Ivatt Class 4 mogul was made by  B Clark and is photographed here at the Harrogate exhibition in 2011. Often smaller gauge locomotives are overshadowed at exhibitions by those built to larger scales. But not this one. The quality of the build and finish stood out.

Mr Clark started the engine some 14 years ago when a friend acquired some sketchy outline drawings, and he continued to work steadily on it. The Class 4 was chosen for its looks and because it had not been the subject of many models. A commercial Class 4 design has since appeared - too late for Mr Clark.

Dimensions and detail were obtained by measuring the only preserved loco in the class, on the Severn Valley Railway, and from old photos. The short-lived double chimney version was chosen “as I believe it appears more handsome and gave a more powerful image.”

Many parts were adapted from other designs. For example, cylinders are a modified version of the Jubilee Tank design, in gunmetal with bronze pistons and PTFE rings. Jubilee wheels were also adapted by modifying the weights, and the valve gear is similar to Jubilee but with shortened connecting rods.

Boiler was built in copper and silver soldered, based on the Standard Class but altered to suit. That double chimney is a much modified Hielan Lassie casting.

Tender chassis design is from Martin Evans’ Class 2, with the upper superstructure for a Class 4.