The programmes

Grid reference: HU 3816 9150

Filmed 5-19 October 2003, first screened 27 June 2004

Living on the Edge

Until the Extreme Archaeology team arrived to solve the long-standing mystery of the rectangular structures on the Kame of Isbister, no archaeologist had ever carried out an excavation there. The Kame, which means rocky point or promontory, is a jagged stack of rock off the north coast of Shetland and one of the most remote archaeological sites in Britain. Almost impossible to view from the shore, the site can only be approached by a narrow and eroding arête, or ridge, restricting access to skilled climbers and suicidal sheep.

Enigmatic rectangular earthworks adorn the Kame. They look like the remains of buildings, but beyond that, their function is unknown. Different theories about their origins have suggested that they could date from Shetland's Iron Age past; that they might be part of an early Christian monastery; and that they might be the last traces of an unfortunate leper colony.

But despite the fact that they've fascinated archaeologists for a hundred years, only two people appear to have attempted the treacherous journey to investigate them. The first, back in 1877, was a theology student, who carried out a small investigation and described and mapped the site. The second was the archaeologist, Raymond Lamb, who carried out a surface survey in 1970.

It's easy to see why so little is known about the site. Guarded by 50-metre high sea cliffs and frequently lashed by gale-force winds and storms that are constantly eroding the site, it's hard to imagine what brought the Kame's early inhabitants here in the first place.

The team faced one of their toughest expeditions of the series just to get onto the Kame. A treacherous knife-edge ridge incorporating severe rock faces connects the stack to the mainland, and the danger is apparent early in the programme, when the cameraman films his own fall from the rock and is saved only by his safety ropes.

Once on the stack, the mission seems simple: to survey and excavate the rectangular earthworks to discover when and why they were built. But in relentless storm conditions, and with each team member exhausted and having to stay harnessed up for safety, digging a trench is an arduous process. The archaeological results turn out to be worth it, though, as the team solves at least part of the mystery of the earthworks – and reveals some unexpected inhabitants.

What they found

The remains on the Kame of Isbister are a scheduled ancient monument and any excavation of such sites has to be approved by Historic Scotland. Because archaeological excavation is an inevitably destructive process, strict limits were imposed on how many trenches could be dug. Extreme Archaeology was allowed to excavate just eight square metres in total.

This added to the frustration of the archaeologists as one trench after another failed to reveal any finds with which to date the structures. The absence of any fragments of pottery, in particular, caused lead archaeologist Katie Hirst to speculate that the site might have been a monastic retreat of some sort rather than a centre of habitation.

The structures seemed to be too big, well built and numerous to support this theory, however. The method of construction of the buildings and a boat-shaped mound, typical of Viking burials, pointed towards a Viking settlement of some sort. But without firm dating evidence, this could be no more than another theory.

With no pottery or other remains found on the site, the only hope of dating the structures lay in the small amounts of charcoal found on a burnt surface excavated by Katie Hirst. Samples of the burnt area were taken for carbon-14 dating, a method that can date organic remains by measuring the decay of radiocarbon atoms, which takes place at a constant rate. Because there was less than 4% charcoal in the soil sample, the sample was tested using a process known as accelerated mass spectrometry in order to get an accurate date.

This revealed that the charcoal remains dated from 865 AD – a time when not only were the Vikings establishing settlements on the islands and coasts of Scotland but were also beginning to convert to Christianity. Perhaps the structures on the Kame of Isbister represent an early Viking Christian community.