Summary

An Iron Age slight univallate hillfort.

Source: Historic England

Details

Grimsbury Castle is a slight univallate hillfort and also a promontory fort of 3.2 hectares (8 acres) almost entirely covered in trees. It has an inner bank, outer ditch and counterscarp bank as well as an outwork, comprising a bank, to the west of the hillfort. The hillfort is roughly triangular in plan, generally following the contours of the hill. The apices of the triangle are to the north, south-west and south-east. Height from bottom of ditch to top of bank is generally 2m or more.

The western outwork curves in an arc protecting the western side of the hillfort at a distance of between 40m and 60m from the counterscarp bank of the hillfort.

ENTRANCES
There are two obvious entrances, both of which have associated outworks; the most elaborate is the western entrance where the hillfort’s bank and ditch are inturned slightly leaving an access of about 11m at its narrowest point. Here the inner bank is 2.5m high and the counterscarp bank to about 1m high. About 30m to the west of this entrance is the remains of an outer entrance work, part of the western outwork, comprising a complex of banks and a banked ditch about 2.5m deep. Such outworks are reasonably rare. This outer entrance work adjoins the western outwork bank which stands to about 1m high. The entrance in the northern apex of the hillfort triangle is about 11m wide and accommodates a modern road which follows the line of the original holloway rising uphill from the north. This original holloway can be seen as a 2m high double bank and ditch following the line of the modern road. It becomes a double ditch as it approaches the hillfort.

OUTWORK
The outwork to the west is thought to be of two periods of construction, the northern, and apparently earlier, part appears as a slight break in slope to 1m high and is thought to possibly be associated with enclosing stock, whilst the southern section is a substantial bank to 1.5m high and clearly of a defensive nature.

EXTENT OF SCHEDULING
The scheduling aims to protect the full known extent of the hillfort including its interior, its banks and ditches and the western outwork. The maximum extent of the monument is about 547m NE-SW by about 400m NW-SE. A 5m margin is included for the support and protection of the monument.

A number of features are excluded from the scheduling; these include all roads and their make-up, The Folly (Lodge) and its outbuildings and all signs and notice boards, although the ground beneath them is included.

Source: Historic England

Reasons for Scheduling

The slight univallate hillfort known as Grimsbury Castle is scheduled for the following principal reasons:
* Survival: the hillfort survives well with earthworks to over 2m high;
* Potential: only a small part of the hillfort has been excavated so that there is extensive archaeological potential remaining for future investigation. This hillfort also has the potential to help understand the transition between Bronze Age and Iron Age communities;
* Rarity: slight univallate hillforts are rare, there being only about 150 examples surviving nationally.

Source: Historic England

Sources

Books and journals
'Journal of the british Archaeological Association' in 15th Sept - Grimsbury, , Vol. 16, (1860), 229-30
Wood, P, 'berkshire Archaeological Journal' in The Early Iron Age Camp Called Grimsbury Castle, Near Hermitage, (1959)

Source: Historic England