Grimsbury Castle Hill-fort, Berkshire

Grimsbury Castle is an Iron Age contour hillfort constructed on a promontory. It encloses around 8 acres (3.2 hectares) of the plateau, and includes a substantial outwork around 80 metres outside the western defences. On the whole the ramparts are in good condition, and exceed 10 ft (3 metres) in height when measured from the base of the ditch. A road bisects the hillfort, allowing the visitor to drive through the defences.

By following the contours of the hill, the builders of Grimsbury Castle have produced an irregularly shaped hillfort not dissimilar to the oak-leaf shaped Caesar’s Camp.

There are three possibly original entrances. The one in the west is slightly inturned and shows traces of a holloway approach. The second, in the northern rampart, is wider (approx. 24 yards, or 21 metres), and also approached by a holloway. The third entrance is of a slightly more questionable nature, consisting of an undug stretch a little way from a nearby group of springs. (1)

In the late 1950s Peter Wood conducted an excavation here, which consisted of a five ft (1.5 metre) wide trench cutting across a section of the eastern defences. Finds were scarce, but included a few sling-stones, some possibly Mesolithic flint artefacts, a portion of an Iron Age beehive quern, and some fragments of pottery ascribed to the latter part of the Early Iron Age. (2)

Six or seven pillow mounds (Medieval man-made rabbit warrens) were excavated at some point in the 19th century, but nothing of interest was discovered. (3)


OS map reference: SU 5109 7221. Nearest town/village: Hermitage.


(1) Aylwin Cotton, M. (1962). Berkshire Hill Forts. Berkshire Archaeological Journal: vol. 60: 30-52

(2) Wood, P. (1959). `The Early Iron Age Camp called Grimsbury Castle, near Hermitage, Berks’ Berks AJ 57 74-82 [Note by Cotton, Mrs M Aylwin S]

(3) English Heritage National Monument no. SU 57 SW 6.

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