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.

The castle was located slightly away from the main road, to give additional space for the earthworks involved, and was positioned as to benefit from natural springs running down from under the hill.
It had a motte and bailey design, with a 40 foot (12 m) high motte, and a bailey around 500 foot (150 m) by 300 foot (91 m), enclosing 0.6 acres (0.24 ha) acres.
A double bank and ditch ran around the whole castle, with both sets of ditches filled with water.
In total, the wider earthworks occupy around 11 acres (4.5 ha).
A fossarius – a specialised ditch digger – was recorded as being employed maintained at the castle in 1086.
Radiocarbon dating of organic remains from within the castle's motte indicates a post 1066 construction date.

A large deer park, owned by the Crown, was established around the castle to provide hunting grounds.
The castle was carefully positioned next to the park, which was overlooked by the motte.
A vineyard was also maintained alongside the castle.
The old Anglo-Saxon manorial centre was moved to the site, and as a result the Anglo-Saxon settlement of Berkhamsted may have shifted from the area now called Northchurch along Akeman Street to be closer to the castle; several mills, essential for grinding flour, were present there in 1086.

Robert's son, William rebelled against Henry I and the castle was confiscated.
Henry granted Berkhamsted to his chancellor, Ranulf.
In 1123, however, when Ranulf was travelling to the castle with Henry, the chancellor rode over the nearby hill, became overly exhilarated at the view ahead of him and fell off his horse, dying from his injuries.

The castle was subsequently given by Henry II to Thomas Becket when he became chancellor in 1155.
Becket extended the castle to accommodate his large household, but fell from favour in 1164 and the castle was confiscated by the king.
Henry II liked Berkhamsted and subsequently used it himself extensively.
By the mid-12th century, the castle had been rebuilt in stone, probably by Becket, with a shell keep and an outer stone wall; the bailey was divided in two by a wall to form an inner and an outer bailey.
A gatehouse led down into the town, meeting with Castle Street.
Henry II also officially recognised the surrounding settlement of Berkhamsted as a town in 1156.

Under King John the castle was part of the lands forming the jointure of his second wife Isabella.
John entrusted the castle to Geoffrey Fitz Peter in 1206, who rebuilt much of the town.
Geoffrey died in 1213 and the castle passed to his son, John Fitzgeoffrey.

Political tensions in England began to rise, however, and a potential conflict between King John and an alliance of rebel barons opposed to his rule began to look likely.
In early 1215, King John installed a trusted German mercenary called Ranulph in charge of Berkhamsted Castle and reviewed the defensive arrangements there that April.
Civil war broke out later that same year.
Initially, the rebels were hampered by a lack of equipment – in particular, siege engines – but in May 1216 the future Louis VIII crossed over the English Channel joining the rebel cause and being proclaimed king in London, bringing with him heavy siege equipment.

King John died in October, and in December Louis besieged Berkhamsted Castle.
The prince deployed his siege engines, probably trebuchets, and attacked the castle repeatedly for twenty
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. 
The castle was located slightly away from the main road, to give additional space for the earthworks involved, and was positioned as to benefit from natural springs running down from under the hill. It had a motte and bailey design, with a 40 foot (12 m) high motte, and a bailey around 500 foot (150 m) by 300 foot (91 m), enclosing 0.6 acres (0.24 ha) acres. A double bank and ditch ran around the whole castle, with both sets of ditches filled with water. In total, the wider earthworks occupy around 11 acres (4.5 ha). A fossarius – a specialised ditch digger – was recorded as being employed maintained at the castle in 1086. Radiocarbon dating of organic remains from within the castle's motte indicates a post 1066 construction date.
A large deer park, owned by the Crown, was established around the castle to provide hunting grounds. The castle was carefully positioned next to the park, which was overlooked by the motte. A vineyard was also maintained alongside the castle. The old Anglo-Saxon manorial centre was moved to the site, and as a result the Anglo-Saxon settlement of Berkhamsted may have shifted from the area now called Northchurch along Akeman Street to be closer to the castle; several mills, essential for grinding flour, were present there in 1086.
Robert's son, William rebelled against Henry I and the castle was confiscated. Henry granted Berkhamsted to his chancellor, Ranulf. In 1123, however, when Ranulf was travelling to the castle with Henry, the chancellor rode over the nearby hill, became overly exhilarated at the view ahead of him and fell off his horse, dying from his injuries. 
The castle was subsequently given by Henry II to Thomas Becket when he became chancellor in 1155. Becket extended the castle to accommodate his large household, but fell from favour in 1164 and the castle was confiscated by the king. Henry II liked Berkhamsted and subsequently used it himself extensively. By the mid-12th century, the castle had been rebuilt in stone, probably by Becket, with a shell keep and an outer stone wall; the bailey was divided in two by a wall to form an inner and an outer bailey. A gatehouse led down into the town, meeting with Castle Street. Henry II also officially recognised the surrounding settlement of Berkhamsted as a town in 1156.
Under King John the castle was part of the lands forming the jointure of his second wife Isabella. John entrusted the castle to Geoffrey Fitz Peter in 1206, who rebuilt much of the town. Geoffrey died in 1213 and the castle passed to his son, John Fitzgeoffrey. 
Political tensions in England began to rise, however, and a potential conflict between King John and an alliance of rebel barons opposed to his rule began to look likely. In early 1215, King John installed a trusted German mercenary called Ranulph in charge of Berkhamsted Castle and reviewed the defensive arrangements there that April. Civil war broke out later that same year. Initially, the rebels were hampered by a lack of equipment – in particular, siege engines – but in May 1216 the future Louis VIII crossed over the English Channel joining the rebel cause and being proclaimed king in London, bringing with him heavy siege equipment. 
King John died in October, and in December Louis besieged Berkhamsted Castle. The prince deployed his siege engines, probably trebuchets, and attacked the castle repeatedly for twenty
Berkhamsted Castle