 Berkhamsted Castle was built during the Norman conquest of England in 1066 . After William the Conqueror defeated the Anglo @-@ Saxons at the Battle of Hastings he advanced from the coast , across the Thames Valley and north into Hertfordshire . Chroniclers suggest that the Archbishop of York surrendered to William in Berkhamsted , and William probably ordered the construction of the castle before proceeding south into London . Berkhamsted was strategically significant , as it lay on a key route into the Midlands from London through the Chiltern Hills . The actual construction work was probably overseen by William 's half @-@ brother , Robert of Mortain , who owned it by the time of the writing of the Domesday Book . 
