This is a long ditch or bank near Aldworth, running over the boundary into what is now Oxfordshire; it may date from the Iron Age or from the early medieval period. Another site nearby is Grimsbury Castle, a prehistoric hill-fort which similarly takes its name from the mysterious Grim, who appears in many parts of English as a legendary creator of large-scale linear ditches. In most cases, the feature has the alternative name of Devil’s Ditch, so it may be that ‘Grim’ was simply a euphemism used by those who thought it dangerous to mention the devil openly. On the other hand, as has often been pointed out, it could be a nickname for the Anglo-Saxon god “Woden” (as Grimnr, meaning ‘hooded’, is for his Norse equivalent, Odin). Although there are no narrative myths presenting Woden/Odin as a creator of landscape features, the occurrence of the name Wansdyke in Wiltshire proves that this was indeed one of the powers ascribed to him, for this name is derived from Woden’s Dyke.
However, the story told here in recent centuries has forgotten Grim, and features the Devil instead. It is said that he ploughed the whole length of the ditch in a single night, helped by one of his imps; two round barrows nearby were formed when he stopped to scrape off the mud clogging the ploughshare, and a smaller mound was a clod of earth he threw at the imp for driving crooked and casting a kink in the ditch.