Dug for defence or, more commonly, to mark the boundary of an estate. The dykes of the prehistoric, Roman and Anglo‐Saxon periods were immense linear earthworks running for miles. Smaller ditches were dug along the boundaries of manors, townships, and estates, around the perimeters of open fields, or to separate commons, woods, or deer parks from cultivated land. They can sometimes be traced as landscape features or on a large‐scale map with the assistance of minor place‐names. In the 19th century ditches were dug on grouse‐shooting moors to stop the spread of fires.