Concentric Earthworks
Geoff Leet

Large concentric earthworks exist in the far North of Scotland which are similar to the Boath ringwork near Nairn which is known to have been used by William the Lion in AD 1185 as a royal castle, (and described by Mike Salter in THE CASTLES OF WESTERN AND NORTHERN SCOTLAND, Folly Publications).

Earthworks would have been much more vulnerable to the plough than the many Brochs which are known to have been lost, so earthworks may well have been far more numerous in the past.

Concentric earthworks (some with Brochs inside) were surveyed by selecting the most complete diameter and measuring by tape. The horizontal sizes are accurate to about 100mm and the vertical measurements within say 300mm. The dates of the concentric earthworks are unknown. They are clearly of a different scale to the great tribal hill forts of Garrywhin or Dorrery and more similar in area to the smaller promontory forts. If the earthworks are older than the Brochs, say 150 BC, some Brochs may have been built within existing earth rings. About half the Brochs stand within rings like the examples shown. If the earth rings were later than the Brochs our choice of possible builders could vary from garrisons of Picts to Normans.

THE FAMOUS FIVE (In diminishing order of size)

The Ring of Castlehill, Lyth, is now defended by a swamp. In the Royal Comission on the Ancient and Historical Monuments of Scotland, Eric Talbot suggests a Norman campaign castle related to William the Lion (see above), or a Norse defence like one stage of Cubbie Roo's castle, AD 1150, on Wyre, Orkney.

The Borg at Borgie is on hard heathery ground and the deep moat is crossed by two wide causeways.

The Ackergill Duck Decoy was used for shooting wildfowl in Victorian times. The shape provides poor fields of fire so I assume that an older structure was pressed into service.

The Foxes Mound, Killimster, has been damaged by quarrying. The surrounding ground is now a wet bog. Bog grew rapidly about 1500BC so the heather may be later than the Mound.

Langdale, Strath Naver, is close to the road but disguised by an 19th century sheep fank wall. It featured as a shelter for the sailors from the Hazard, captured with the gold for Prince Charles at Melness and Loch Haken in 1745.

Rinsary, Berridale, is probably unfinished, not very circular, and is too small to include with the FIVE. A futher mound near the Loch More dam is mentioned by Eric Talbert in Caithness Field Club Bulletin 1.6 (Oct 1977) but is too damaged to measure.

Only excavation could provide dates and prove that these rings are a single class of forgotten monuments. If the rings were early and if Brochs were commonly built within them, concentric earthworks may turn out to have been very numerous indeed.

Published 1997