Seventy-one years ago, a schoolboy in Scotland was digging up potatoes as a punishment when he discovered an ancient Egyptian statue — the first in a collection of ancient Egyptian sculptures and artifacts buried in the grounds of his school. Now, researchers have finally worked out how the artifacts got to the British Isles.

Between 1952 and 1984, several antique statues were found on the grounds of Melville House — a stately building in Fife county that lodged soldiers during World War II and later served as a boarding school. Teachers and pupils brought each new discovery to museum curators and experts, who identified the statues as ancient Egyptian artifacts, but no one could figure out how they had ended up there.

“This is a fascinating collection, made all the more so by the mystery surrounding its origins in this country,” Margaret Maitland, principal curator of the Ancient Mediterranean at National Museums Scotland where most of the objects are housed, said in a statement.

The ancient collection includes a nearly 4,000-year-old statue head carved out of red sandstone, which Maitland described as a “masterpiece of Egyptian sculpture,” as well as several bronze and ceramic figurines dating to between 1069 B.C and 30 B.C., or just before the Romans took over Egypt as a province.

“Excavating and researching these finds at Melville House has been the most unusual project in my archaeological career, and I’m delighted to now be telling the story in full,” Elizabeth Goring, a former curator at the Royal Scottish Museum in Edinburgh (now the National Museum of Scotland), said in the statement.

Previous efforts to determine the origin of these objects were fruitless, but researchers now think they were brought there by Alexander Leslie-Melville, whose title was Lord Balgonie — a young heir to Melville House who traveled to Egypt in 1856 and died one year later upon his return to the U.K.