IT has long been regarded as the cradle of Christianity in Scotland, where the earliest missionaries gathered before spreading the Word of the Lord across the land.

But now archaeologists have uncovered fascinating new evidence of those who lived on the island of Iona long before St Columba set foot on its shores during preparatory work for the building of an extension to the small school.

The Hebridean Isle is home to a religious community, with an abbey founded in 563 by St Columba and 12 companions who had been exiled from his native Ireland.

Yet when they arrived they would have already found an existing population with a recent dig revealing traces of buildings which take the island's history back 2,500 years.

And it seems as though they lived in decidedly un-Christian times with the remains of a two-metre defensive wall found among other remnants of Iona's long vanished past.

Excavations have also revealed pottery, flints and other prehistoric material, indicating a prehistoric village.

Archaeologist Hugh McBrien, of the West of Scotland Archaeology Service, an umbrella organisation providing expertise to 13 local authorities, described the finds as "exciting".

He said: "When finds like this come along it allows the past to speak to us. There are no written records, of course, so all we have to go on is what is in the ground.

"When we find something unexpected, as in this case, we have to stop and reconsider what we previously understood about the site.

"What is becoming clear is that when the ice sheets rolled back off Scotland some 1012,000 years ago the Mesolithic hunter gatherers moved onto the islands and followed the retreating ice.

"What we now have on Iona is evidence that people lived on the island, created boundaries and set up communities long before the lands were 'discovered' by St Columba."

The archaeological work was carried out by Dr Clare Ellis of Campbeltown-based professional archaeology company Argyll Archaeology Ltd.

Dr Ellis's team discovered two different periods of building on top of the original village mound of more than 1,000 years, and a previously unknown extension to the medieval vallum, or wall, has all been found in a shallow ditch next to the school.

She said: "The remains of a turf bank with a cobble base can also be clearly seen. This bank is on the same alignment as the ditch, though it is notable that it has been cut by the ditch, indicating that it pre-dates this feature.

"It seems very likely that the turf bank and ditch are early medieval in date, perhaps 7th or 8th century, and may represent the remains of an unknown monastic boundary, while the underlying soils appear likely to date from the late Bronze Age or Iron Age.

"What is most exciting to me is that the lines of the property that exist now are very similar to the property lines that existed more than 2,000 years ago."

To allow work on the school extension to proceed, the finds will be recorded, samples removed and the site then covered over with concrete, with remains being preserved and stored.

Dr Ellis said she was keen to get back onto the site later in the year and carry out further investigations when when septic tanks are due to be put installed.