The original purpose of the ground is unclear, although local legend suggests that it was part of a salt making industry run by monks from the adjacent Cluniac Lewes Priory, the ruins of which can still be seen from the ground.
Indeed, the ground may merely be the excavation pit for the Mount itself, which has been suggested as the original 'temporary' motte and bailey fortress constructed by William the Conqueror's close ally, William de Warenne, before he developed Lewes Castle on higher ground.