In 1955 specific open wagons for the conveyance of China Clay were constructed at Swindon Works, and from 1974 the whole fleet of around 900 wagons were modified when a metal bar was added to raise the tarpaulins that were used when the wagons were loaded to protect the cargo, giving them the nickname "Clay Hoods". These 5-plank wooden open wagons, designated UCV, had 4 wheels with a wheelbase and vacuum brakes, and in the early 1970s the heavier freight trains to and from Carne Point were typically made up of these wagons hauled by Western diesels while lighter loads were hauled by smaller Type 2 diesels, initially Class 22 hydraulics and then later by Class 25 diesel-electrics. Following the retirement of these classes of locomotive in the 1980s, trains of "Clay Hoods" were typically hauled by Class 37s and while from 1988 the old open clay wagons were replaced with 45-ton CDA hoppers with air brakes, into the 1990s the trains continued to be hauled by class 37's shedded at St Blazey.