Excavations at St John's College in the heart of Oxford have dramatically altered our view of the prehistoric landscape, provided striking evidence of a massacre dating to around AD 1000, and shed light on the later occupation of the site: a suburb in the medieval period and later a farm.The earliest feature was a massive ditch interpreted as part of a henge. Its diameter of just over 150m places it in the monumental class, of which only around 20 are known in Britain. These large henges are often the focus of a wider ritual landscape. The chronology of the henge can be traced from its construction at the end of the late Neolithic, up to the time when it disappeared as a major feature in the landscape in early medieval times.Of particular significance is the discovery of at least 35 human skeletons, tumbled together into the depression left by the henge ditch. All were adult males, except two adolescents, all had met a violent death, many having been mutilated besides, and some partially burned. The evidence points towards these men being Danish victims of King Aethelred's decree ordering their extermination in AD1002.