In Arundel, West Sussex. The original structure (motte and bailey) was built in 1068, during the reign of William the Conquerer, and was subsequently expanded.
Arundel Castle saw action during the English Civil War (1642-45) as it was twice besieged, first by Royalists who took control, then by Cromwell’s Parliamentarian force led by William Waller. The second siege was short lived (two weeks) as the Parliamnetarian forces simply drained the lake outside, for which the Castle depended upon for fresh water, forcing the Royalists to surrender – a slight flaw in the Castle’s design!
The Castle is now the principal seat of the Duke of Norfolk and his family.