[1][2] At the time of its construction, it would have constituted an island of firm soil surrounded by waterlogged fens.

[1][2] During this time period the Norman forces were combating a local revolt under Hereward the Wake, and the hillfort would have been strategically located on the Aldreth Causway, the main road to Ely.

[1][2] A postulated name of "Belassise", from the Old French "bel assis" (meaning well seated/placed), also suggests a Norman link.

[6] The importance of this location in the defence of Ely has led some to suggest that the ringfort may have been the Castle of Aldreth.

Eventually, the Norman troops bribed a local monk to show them a safe passage across the fen.