The only remaining visible signs of the old castle are the large mound of the motte, and traces of the wall that surrounded the bailey.

He was a kinsman of Hugh d'Avranches, Earl of Chester and the castle was designed to consolidate Norman advances into the north of Wales at the command of William the Conqueror.

Using this castle as a base, Robert subdued the Welsh and established control of much of North Wales.

A borough became established beside the castle and by 1086, eighteen burgesses enjoying special privileges lived here, and the buildings included a church and a mint.

Tradition has it that Twthill Castle was built on the site of the palace of Gruffydd ap Llywelyn, king of Wales.