Gilbert de Clare's Treasure Tower dated from 1289 and housed his revenues.

It was later supervised by his illustrious wife and widow, Joan of Acre, daughter of Edward I. It housed "a dog called Coker" which may be the first reference to a cocker spaniel.

Glyndwr's army would have been seen from here, as it beseiged the Castle before the Battle of Usk (Pwll Melyn) of 1405.