 The ruins of the keep are situated on top of this mound in the central area.It was excavated by Martyn Jope and R. I. Threlfall in 1946–1947 and then in 1959.Excavations carried out in 1946–1947 not only unearthed a number of important artefacts such as 12th century shelly ware pottery, they also showed how earth was piled up around the outside of a square tower for fortification i.e the castle was built on ground level and then the clay mound, that survives to date, was built around it, instead of the castle being built on a raised mound from the start.