[1] A fragment of the castle remains and is a Grade II listed building.

[2] It was named after Roger d'Oilly who was granted it by William the Conqueror and whose brother built Oxford Castle.

Excavations carried out in 1946–1947 not only unearthed a number of important artefacts such as 12th-century shelly ware pottery,[1][5] 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.

[6][7] Whilst an uncommon practise, similar examples of this style of construction can be found at Lydford, Caldicot, and Skenfrith, amongst others.

[10] These two castles are considered unique, as they are in close proximity, being only 550 metres (1,800 ft) apart, yet they have never been used in armed struggle against each other.