As a consequence he was deprived of his lands, including the castle and its area, and titles by Stephen after 1138, when he fled into exile.
This was short-lived; on the accession of Henry II in 1154, William FitzAlan recovered his estates and was restored as High Sheriff of Shropshire in 1155 until his death in 1160.
The internal layout of the keep is not known, but an inventory compiled in 1398 notes three chambers, hall, chapel dedicated to St Nicholas, kitchen, larder and buttery.
To the south east of the keep are the remains of a bastion, largely rebuilt in the late 19th century, it is a Grade II Listed Building.
The castle bailey, which lies to the south of the motte, probably served as the initial focus for the development of the town.