Archaeologists have located one of the most important buildings in the history of Western European Christianity – but it’s not a vast cathedral or an impressive tomb, but merely a humble wattle and daub hut on a remote windswept island.

Using radiocarbon dating techniques and other evidence, the scholars – from the University of Glasgow – believe they have demonstrated that the tiny five-metre square building was almost certainly the daytime home of early medieval Scotland’s most important saint, St Columba.

Located on the island of Iona, off the west coast of Scotland, the unprepossessing hut was probably the first administrative hub of the monastic community he founded – and whose monks, over succeeding centuries, went on to establish similar monasteries in mainland Scotland, in north-east England, in Belgium, in France and in Switzerland.

During much of the Dark Ages, Iona was of critical importance in spreading knowledge, literacy, philosophical ideas and artistic skills throughout large areas of western Europe.

It was probably at Iona that the world’s most famous early illuminated manuscript, the Book of Kells, was produced – and it was from here that the epicentre of early northern English Christianity, the monastery of Lindisfarne was founded.

The story of the discovery of St Columba’s hut is a long but significant one.

For centuries, local Gaelic folk tradition seems to have held that a natural grass-covered rock outcrop (known as the Tòrr an Aba) was specifically associated with an important abbot. What’s more that rocky knoll fitted a late 7th century account describing the location of St Columba’s hut.

Then in the 1950s, a British archaeologist called Charles Thomas excavated the outcrop and found the burned remains of a wattle and daub hut under a layer of earth and pebbles. He was convinced that it was Iona’s great founding abbot, Columba’s writing cell.

But most scholars did not believe him. It was felt that the evidence was not strong enough and that the hut probably dated from many centuries after St Columba’s time. In 1957, when Thomas found the hut’s burned wood remains, radiocarbon dating had only just been developed the previous year and was in its infancy and very expensive.

The crucial charcoal was therefore not dated and remained for the next 55 years in a series of matchboxes, first in a succession of storerooms and finally in his garage – but in 2012, he donated them to Historic Scotland (now Historic Environment Scotland).

Then earlier this year two Glasgow University archaeologists - Dr Adrián Maldonado and Dr Ewan Campbell - arranged to have them radiocarbon dated at the Scottish Universities Environmental Research Centre .

The results were extraordinary. They demonstrated that the hut was not a later structure – but did indeed date, in line with Thomas’ theory, to somewhere between 540 and 650 AD. St Columba was Abbot of Iona from the date of the monastery’s foundation (563 AD) till his death (597 AD).

Additional new evidence shows that, at some stage after his death, a monument (a large cross) was erected on the site of the hut, presumably to commemorate the life and work of the monastery’s famous first abbot.

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What’s more, new radiocarbon investigations by the two Glasgow archaeologists are revealing that, potentially at around the time that monument was built, the Iona monks created what may well be Britain’s very earliest pilgrims road, pre-dating the famous pilgrims route to Thomas Becket’s tomb in Canterbury (made famous by Chaucer’s Canterbury Tales) by up to four centuries.

The archaeologists are currently investigating the possibility that Iona’s pilgrimage route (known for centuries as the Street of the Dead) may have been loosely based on Jerusalem’s Via Dolorosa (the Street of Pain) along which Jesus is said to have walked to his crucifixion.

Significantly, around a century after Columba’s death, his biographer (a monk at Iona called Adomnan) also wrote an account and description of the Christian holy places and pilgrimage destinations of Jerusalem – so we know that Iona’s monks would have been well aware of the concept of pilgrimage.

It’s thought that Iona’s possible version of that Jerusalem prototype was eventually up to 600 metres long and, by the 9th century, may have started at the island’s Bay of the Martyrs (potentially, the site of a terrible massacre of Iona’s monks, carried out by the Vikings in 806) and ended at the tomb of St Columba (where the current abbey is located). Along the route, pilgrims would have passed through a graveyard of monks (possibly including those monks who were martyred by the Vikings) – and by the side of a chapel dedicated to a particular colleague of St Columba who, according to legend, was buried alive by his more normally saintly abbot!

This seemingly unfortunate monk, St Oran – is said to have selflessly volunteered to be buried alive by St Columba as a foundation sacrifice to ensure success in building an important chapel within the monastic complex. The story seems improbable, as human sacrifice would have been anathema to pious Christians like Columba.

However, it is conceivable that the story was inherited from a pre-Christian phase of Iona’s story. Some evidence from around the monastic complex hints at the possibility that it may previously have been a high status or even royal pagan religious site – where such human sacrifices might well have been carried out.

Finally, just before the pilgrims would have arrived at St Columba’s tomb, they would have passed three large sculpted stone crosses (each only around 5 m from the next), commemorating the lives of St Martin, St Matthew and St John.

Commenting on the hut date findings, Glasgow University archaeologist, Dr Adrián Maldonado, said: “This discovery is massive. St Columba is a key figure in Western Christendom.

“We were granted access to the original finds from Charles Thomas, and we could work on his notes and charcoal samples which were excavated in 1957. Luckily Thomas kept hold of them, as he knew they were important, and because they were kept dry, they were still in a good condition.

“Thomas always believed he and his team had uncovered Columba’s original wooden hut, but they could never prove it because the technology wasn’t there. Radiocarbon dating was in its infancy, it had only been discovered a year earlier in 1956, so there was not a lot they could do with the samples.

“So for us, 60 years later, to be able to send the original samples off to the radiocarbon dating labs and have them come back showing, within the margin of error, as something which may have been built in the lifetime of St Columba, is very exciting.

“This is as close as any archaeologist has come to excavating a structure built during the time of St Columba, and it is a great vindication of the archaeological instincts of Thomas and his team. It is a remarkable lesson in the value of curating excavation archives for as long as it takes, to make sure the material is ready for the next wave of technology.”

The research project has been carried out by the University of Glasgow, supported by Historic Environment Scotland and the National Trust for Scotland.

Professor Thomas Clancy, Celtic and Gaelic historian at the University of Glasgow, said: “The results of the radiocarbon dating are nothing short of exhilarating. The remains on top of Tòrr an Aba had been dismissed as from a much later date. Now we know they belonged to a structure which stood there in Columba’s lifetime. More than that, the dates, and our new understanding of the turning of the site into a monument not long after its use, makes it pretty clear that this was St Columba’s day or writing house. From here, he oversaw the day-to-day activities of his monastery”.