A north-north-west to south-south-east aligned linear earthwork, interpreted as a medieval earthwork constructed across a shallow sandstone valley. The earthwork coincides with the modern Kent-Surrey county boundary and survives for a total length of around 315 metres. It takes the form of a large bank up to 15 metres wide and 3 metres high, flanked to the south west by a ditch up to 9 metres wide and 1.5 metres deep. Towards the north west, the ditch has become infilled during past, modern ploughing and survives as a buried feature. The south eastern end of the earthwork is formed by a well-defined, rounded terminal, whilst the original north western end has been destroyed by post-medieval sand extraction. The central part of the monument has been damaged by the construction of an embankment for the modern A25 between Limpsfield and Westerham. The linear earthwork is thought to have been constructed between the fifth and eighth centuries AD, when it is likely to have formed a strategically important part of the boundary between rival Anglo-Saxon kingdoms. It was designed to control the communication route which linked the two territories.