The Old Man of Hoy, the famous 140m rock stack that rises out of the sea in the Isles of Orkney, off the north coast of Scotland, is well known as a magnet for adventurous climbers. Less well known until now, however, was that people lived atop some of these rocky towers, far above the sea and separated from the island.

Recent excavations have uncovered part of an unconventional Viking Age village on the top of another Orcadian sea stack known as the Brough of Deerness, lying at the eastern extremity of Mainland, Orkney’s principal island. At 30m high and 80m across, it is an unexpected place to find a 10th to 12th-century church surrounded by the foundations of approximately 30 other buildings.

Fieldwork in the 1970s discovered that the existing ruined church was built on the foundations of an earlier chapel. The two construction phases were separated by an archaeological layer containing an Anglo-Saxon coin minted between 959 and 975, said Dr James Barrett of the University of Cambridge, who directed the new investigation. This find shows that the site is one of the earliest known Christian settlements in the Viking North Atlantic. Intriguingly, the cemetery around the church contained only six graves including five of children, one newborn.

Aerial photography and geophysical surveys show that the rest of the stack is covered with what look like house foundations. To understand this unusual site, and with it the relationship between religious conversion and Viking settlement in Scotland, research has focused on these houses. Dr Barrett explained: “We need to discover whether people really lived up on the stack, and if so for how long. We also need to know who they were and what they were doing there.”

Before the new dig the existing evidence from the Brough of Deerness could have implied either the early spread of Celtic monasticism to the Scandinavian world, or the existence of a Christian Viking principality like that described in the Orkneyinga Saga - a history of the earls of Orkney written in Iceland around 1200. Either would have important implications for our understanding of the role of religion in the Scandinavian diaspora that had a major impact on Viking Age Britain and Ireland.

This summer, in work funded by the McDonald Institute at Cambridge, the Orkney Islands Council, and the Norwegian Government, two building foundations were exposed, both apparently 10th to 11th century in date.

Surprisingly, at least one was clearly a domestic house inhabited for many years. It had been renovated several times and included textile-making equipment and beads, known to be associated with Viking Age women.

Combined with the infant burials previously discovered in the cemetery, this evidence seems to rule out a monastic interpretation. But why would families live in such an extreme location? The excavators discovered just how exposed the site is. Dr Barrett said: “The wood frame of our army tent was turned to matchwood by high winds twice in five weeks. Some of the broken pieces were oak and these are summer conditions!”

Dr Barrett believed that the stack was the defensive settlement of a Christian Viking chieftain. Like later medieval castles on the coast, the extreme location would have provided both safety and a symbol of mastery over land and sea. He noted that there was a large Viking Age rural settlement, excavated by Peter Gelling in the 1960s, at Skaill, on the next big bay south of the Brough of Deerness. The stack may have been a redoubt to which at least the ruler and his family could retreat in time of trouble.

In the 10th and 11th centuries churches were often the private property of wealthy patrons and, given that only six graves were discovered, clearly not everyone who lived at the Brough of Deerness could have been buried in the churchyard. One has to imagine that the infants received the unusual privilege of burial there because of their lineage.

“The Brough of Deerness is a remarkable archaeological mystery, even more so after spending five weeks on the stack”, according to Dr Barrett. “It shows us that, even in the most Scandinavianised regions of Viking Age Britain, power was maintained by eventually accepting the local religion, in this case Christianity.”