The wagons were probably en route back to Ashford PAD following use in connection with weekend track relaying as seen in the appended photo showing work underway to relay the Up Line through Dunton Green station in 1973 (I think). The engineers train is standing on the Down Line and was formed Class 33, several open wagons conveying blanketing material (Meldon Dust / Sand ?), three tank cars, Toad and open wagons loaded with new ballast. In the photo, the blanketing material had already been unloaded and an oil / tar liquid was being sprayed onto it from the tank cars (note open manlid), presumably as a binding agent - hence the involvement of the Soil Mechanics Department. Permanent Way staff can be seen shovelling new bottom ballast from the open wagons beyond the Toad.