An Elizabethan artillery fort built in the mid-16th century, intended to protect warships at the nearby Chatham dockyard. Unfortunately, it entirely failed to do so when in 1667 a Dutch naval raid, under the command of Admiral de Ruyter, sailed up the Medway to attack the dockyard. The enemy fleet met little resistance and left two days later, with the King's flagship as a prize.

It's failure to provide an effective defence was as a result of neglect and a lack of provisions. It subsequently became an ammunition depot, used to resupply warships with guns and gunpowder.