Berkhamstead, formerly also Great Berkhampstead (both: bûrk´əmstĕd, bärk´–), town (1991 pop. 15,382), Hertfordshire, central England. Berkhamstead is mainly residential but has clothing, timber, and chemical industries. It is the site of an 11th-century royal castle in which Edgar Atheling, a claimant to the throne, submitted to William the Conqueror; Thomas à Becket lived in the castle, and Henry II held court there. John II of France was briefly imprisoned in the castle after the battle of Poitiers (1356) in the Hundred Years War. The poet William Cowper was born in Berkhamstead. The town has a remaining 16th-century grammar school.