One of the most spectacular of all the theories recently advanced in archaeoastronomy concerns the standing stones of Carnac in southern Brittany. The possibility that the famous prehistoric megaliths or ‘menhirs’ in this region represent the remains of an extensive, highly accurate lunar observatory has excited much interest in both academic and popular literature. In the company of two experienced archaeologists I recently set out to re-examine and record the field evidence on which the lunar observatory theory is based. The result of this work is to cast serious doubt on the theory, and to illustrate the difficulties of assessing the astronomy of the megalith builders.

In his account of the changes made to the figure of the Cerne Giant by successive cleanings and restorations during the period 1764–1980, Leslie Grinsell refers to the curious lack of documentary references to the Giant before the middle of the eighteenth century, and also makes it clear that, because of the alterations to the figure, dating on stylistic evidence must necessarily be very tentative (Grinsell, 1980). It is the purpose of this article to review some of the major sources of information relating to Cerne Abbas and to consider this remarkable absence of any mention of the Giant. The complete silence of all the documentary sources is of course totally negative evidence and cannot of itself disprove the existence of the Giant; there is no reason why he should have been mentioned in many of the documents since he lay on no boundary and provided no incom e for landowners or their tenants. But the total absence of any reference in all the numerous documents of the sixteenth and early seventeenth centuries must raise a doubt as to whether the figure was there at all; at least it seems likely that the grass had been allowed to grow over him during the later Middle Ages and that he was not re-cut until after the mid-seventeenth century, and a re-cut figure might bear only a vague resemblance to the original, particularly if this had been covered by grass for many years.