BR ordered more than 24000 21t hoppers to several different diagrams over the 10 years from 1949. These wagons were a continuation of a former LNER design, with some of the earliest examples featuring the long brake lever and single-sided brakes of late LNER examples and also riveted bodywork. In common with all coal carrying wagons, they were subjected to the problems of body rot. Between 1971 and 1978 a major re-bodying programme was instituted, with both unfitted and fitted wagons being scheduled for attention.

The Re-Bodied 21t HTV Hopper Wagon Pack features former Diagram 1/146 vehicles that were fitted with roller bearing axleboxes and vacuum brakes along with the new body. Three livery variations are included, in both clean and dirty options: Freight Brown body, with black frames and running gear; Freight Brown body and Frames, with black running gear; maroon body, with black frames and running gear. Empty and Loaded physics options are provided and the loaded examples come with 5 random coal load shapes. There are also 4 random styles of lettering provided to give a bit more variety, as the wagon code was variously rendered as HOP 21 VB, HOP 21 HTV, or just HTV.