It is thought the castle was likely built around 1066, along with other nearby castles in Chichester and Pulborough, to help secure the Norman’s position within Sussex. It was built above the River Rother, a key transport route through Sussex, and was the reason for the development of the town of Midhurst.
It is not certain when the castle was first built, as it does not appear in the Domesday Book. We know that much of west Sussex was given to a friend of William the Conqueror, Roger de Montgomery. In an effort to ensure the Normans could strengthen their rule and stamp out retaliation, Roger de Montgomery built a number of castles, such as the impressive castle that still stands at Arundel.
He also built a number of strategic motte and bailey castles in the area, including one at Chichester in order to control the town and at Midhurst, where there appears to have been no large settlement and therefore was in order to control the crossing of the River Rother and to create a new town.
It was after this that the town around the castle began to flourish, with traders and those who supported the life of the castle settling nearby.
The castle was originally built using wood and earthwork defences until it was rebuilt in stone. The central motte, or mound, used a natural feature that was then heightened with rubble. It is thought this may have been initiated in the mid-1180s by the Bohun family, who had inherited the land.
A circular stone wall reaching up to 1.7m thick was built around the top of the motte. A series of rooms abutted the wall, likely including kitchens, living quarters, storage, stables and a hall. A chapel dedicated to St Denis stood on the site until at least 1367. This gave the hill its original name of St Denis’ Hill, which was corrupted to Tan Hill. This was then further corrected in the 18th century to St Ann’s Hill.
Although the castle appears to have been originally built as a defensive structure, the archaeology seems to suggest that when the castle was rebuilt in stone, its primary purpose was not defence, seen by the simple gate to the inner bailey. Instead, it seems likely it was more of an administrative and domestic castle, whose importance eventually gave way to the new Bohun residence at Cowdray.
The castle was built in its location by Roger de Montgomery in order for a new town to flourish, as he was well aware through previous experience the lucrative nature of a town. Towns generated income through rent and tolls, the majority of which went to the lord of the town.
However, little is known of the exact dates and functions of much of the castle due to a lack of archaeological dating evidence or finds. Initial excavations took place in 1913 by Sir W. St John Hope. Most of the stonework had already been removed at this point in order to build other sites in Midhurst, as well as Cowdray House.
Hope rebuilt some of the walls to aid interpretation of the site at this time. There was said to have been further maintenance of the walls in the 1940s carried out by Italian prisoners of war.
In 1994, Midhurst Town Council commissioned Chichester District Archaeological Unit to carry out work in order to better understand the site for interpretation. This included some trial trenching in an effort to understand which walls were ancient and which had been rebuilt by Hope, and to try to solidify a dating sequence for the site.
Although the castle was eventually abandoned in favour of the Tudor manor of Cowdray House, its existence was integral to the origins of the town of Midhurst. The remains of the motte and bailey, and the foundation walls are now a scheduled ancient monument.