It is well known that the vast majority of stone circles in the British Isles are not actually circles. In fact, there are very few that are truly ‘circular’ in the sense of having a regular, circular ground plan. The shapes can vary from circular, through regular ovals to ovoid, to flattened version of any of these. But there is one form of stone circle that doesn’t fit into any of these categories, that of the ‘Four Poster’.
Four Poster ‘circles’, as their name suggests usually consist of just four uprights, laid on the plan of a circle, sometimes with a fifth recumbent stone. The majority of this type can be found in Scotland, though there are several examples throughout England and some in Ireland. The stones in a true Four Poster are generally placed at the cardinal compass points. Those that have been dated were constructed in the Bronze Age. The English Heritage Monument Class definition describes them thus:
A four-poster stone circle is a rectangular or sub-rectangular setting of four or five stones which are, or were once, upright. The corner stones of the rectangle are usually placed on the perimeter of a good circle, aligned on the cardinal points and are graded in height. The rectangle varies considerably in size from 13m squred to 345m squared. Four-poster stone circles may be recognised in the field as ruined standing structures or from antiquarian sketches. Other components which may be present are cupmarks on one or more of the stones, outlying standing stones, and a mound or cairn within the stone setting.
Four-poster stone circles vary considerably in size, the area enclosed by the rectangle varying from 13m squared to 345m squared. Some appear to have been laid out as a rectangle, others as a circle and some as both. It is the circumferential siting of the stones of four-posters that justifies the otherwise paradoxical use of “circle” for what appears to be a square or rectangle.
Possible examples in Ireland can be found described under ‘Labbamolaga’ and ‘Lettergorman’ on the Irish Megaliths web site. There are also various entries on the Modern Antiquarian and Megalithic Portal web sites describing many of the Scottish circles, many of which are extant in Perthshire. Aubrey Burl, in his book “The Stone Circles of Britain, Ireland, and Brittany” is convinced that the Irish versions of the four-poster model have their design origins in Scotland. The dates for the examples in Perthshire are somewhat earlier than those in SW Ireland, bearing out the possible migration south of the building tradition for this type of ‘stone circle’.
So, the answer to the question in the title: “When is a stone circle not a stone circle?” would appear to be “When it’s a square!”