Eynsford Castle is a rare example of an early Norman 'enclosure' castle, unaltered by later building works. It was built on the site of an earlier Anglo-Saxon fortification in the late 1080s, soon after the Norman Conquest. It was abandoned in 1312 after being vandalised as the result of a family inheritance quarrel.

An enclosure castle is a stronghold, built mainly of stone, that is defended by its walls and towers, rather than from inside a keep or from on top of a motte.