Ten pupils from King Charles's former school, have helped uncover the remains of what archaeologists believe is a medieval Christian church, possibly up to 1,000 years old, on the uninhabited Orkney island of Swona.

The discovery came during a six-day archaeological field trip organised by housemaster Dan McLean, in which students worked alongside professional archaeologists from the Orkney Research Centre for Archaeology (ORCA).

The site was already loosely recorded in Canmore, Scotland's national record of the historic environment run by Historic Environment Scotland, as a rectangular drystone structure roughly 5.5m by 3.5m with walls up to 0.9m thick, known locally as the "Twinly Kirk." However, it had never been properly excavated.  McLean's only real clue going in was a map reference to the ruin.

Digging a test pit and clearing away weeds, the group uncovered a stone step leading to what is believed to have been the church's altar, buried beneath the remains of a later building.

McLean said the construction method, layout and orientation all pointed to a genuine early place of Christian worship: the walls were built dry stone, without clay bonding or mortar, consistent with other Viking-era churches from the 10th and 11th centuries.

If confirmed, the find would be a rare physical trace of Christianity's arrival among Norse settlers in the Northern Isles during the Viking Age, a period in which raiders who had once plundered churches across Britain and Ireland gradually became church-builders themselves, as Christianity took root in Scandinavian communities from the 10th century onward.

McLean told the Press Association: "It was a special moment to confirm to the students that they had helped to uncover a piece of Viking history that could be up to 1,000 years old."

Samples taken from the site will now undergo radiocarbon dating to establish a firmer date and shed more light on the building's history.