1,000-year-old church mystery cracked by students from King Charles' alma mater

Boarding school students in Scotland helped uncover something extraordinary during a school trip: the remains of what's believed to be a .

Young people from Gordonstoun, located in Moray, Scotland, uncovered the foundations of an altar and a step inside the long-known ruins on the deserted island of Swona in Orkney.

Gordonstoun — the alma mater of King Charles III and his late father, Prince Philip — runs an annual service project on the remote island called the Swona Service Project, where students take part in .

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Gordonstoun housemaster Daniel McLean, who is also the organizer of the project, told Fox News Digital the structure had long been known locally as a "kirk," or church, but its origins remained uncertain.

While the ruins themselves were already known, it was unclear whether the structure had actually been a church.

The excavation uncovered altar foundations and a step, lending new weight to a local legend that the ruins were once a church.

The team had surveyed the site the previous year, McLean said, and found several characteristics consistent with early medieval church architecture.

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"Everything about the structure [fit]," he said. "The size of it, the length, the width ratio, the east-west orientation, the location of the door, the construction methods — it all [fit] for it to be an early medieval church."

When the team returned to excavate the site, McLean said they began digging along the inside of the eastern wall, where they believed an altar would have stood.

"I thought if there's anything churchy here, we may find the remains of where the altar was on the inside of the east wall," McLean said.

The team quickly uncovered the foundations of the altar and a step in front of it.

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The church is believed to date to the 10th or 11th century, based on similarities to other Viking-era churches in the region.

For Archie Maclean, one of the students who worked on the excavation, seeing the remains up close made the discovery feel real.

"When you see the altar in person, you go, 'Oh my gosh, it's still after all of this time,'" Maclean told Fox News Digital.

Maclean helped dig the original test pit and later cleaned up the altar and doorway for photographs. He said he was struck by how well the structure had survived.

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"Same with the doorway as well, the structure of the building is still so visible, even after years of earth and wind and weather eroding the outside — I found [it] fascinating personally," Maclean said.

The school has a unique arrangement with the island's owners, the Annal family, and the Swona Heritage Group, to make the experience possible.

The 10 students by bus, ferry and boat to reach Swona, a remote islan