When Viking invaders tore through 9th-century Europe, only one Anglo-Saxon leader was able to withstand their ferocious onslaught. King Alfred of Wessex repelled the attacks and laid the foundations for a kingdom that would become known as England. More than a millennium later, archeologists in Hampshire believe they may have discovered his remains—inside a cardboard box.

For a nation identified so strongly by its rich history of empire, kings and queens, recent years have exposed a decidedly absent-minded approach to royal burials. The latest collection of mislaid remains was discovered 12 months after confirmation that Richard III had been interred beneath a parking lot in Leicester.

Alfred The Great, who was described by historians as “the most perfect character in history,” died in Winchester in 899 AD. He was the only monarch in British history whose name was granted the “Great” sobriquet, and he was the first man referred to as “king of the English,” but after several re-burials after the 16th century it was believed he had been lost in some unmarked grave.

After the shock results of routine carbon dating analysis, it is now thought Alfred, or his son, has spent the last 20 years in a storage box inside the little-known Winchester City Museum. Amateur archeologists dug up the ancient remains in the late 1990s but it was assumed that they belonged to someone who was far more recently deceased.

The extraordinary discovery is the subject of an upcoming BBC documentary, The Search for King Alfred, which will be broadcast next week. Neil Oliver, an archeologist working on the program, said this was one of the most remarkable findings in archeological history. “It overshadows the discovery of Richard III’s remains in my opinion. We are talking about a body of a king more than half a millennia older. He’s one of the few great kings of England that most people can name. He’s a mythologized figure, almost like Arthur,” he said.

Archaeologists carried out an exhumation on a grave at St. Bartholomew’s Church in Winchester, southern England, last March thinking they may have located the ninth-century king. Tests ultimately confounded their theory, which encouraged Dr Katie Tucker, a researcher in human osteology at the University of Winchester, to re-examine some of the other recent excavations in the area.

A dig in the 1990s had uncovered a series of human bones but one was tested and estimated to have come from the 17th or 18th century. “It wasn’t really thought a good use of funding, which wasn’t really available, to date another piece of bone because the date had come back as far later,” Dr Tucker told the Press Association.

She denied that the remains had been forgotten. “It was stored in the museum store with material from hundreds of sites. It was always accessible, it was never hidden away, I was just the first researcher since the excavation that wanted to look at it,” she said.

When tests were carried out on a pelvic bone, the startling scale of the discovery began to emerge. The bone dates back to 895-1017 and belonged to a man aged between 26 and 45 at death. When coupled with the location of the discovery there are thought to be three possible explanations. “The simplest explanation, given there was no Anglo-Saxon cemetery at Hyde Abbey, is that this bone comes from one of the members of the West Saxon royal family brought to the site,” Dr Tucker said.

“Given the age at death of the individual and the probable male identity, the plausible candidates are King Alfred, King Edward the Elder, or the brother of King Edward, Aethelweard. All were buried in the abbey. However, historical evidence indicates that only the coffins of Alfred and Edward were at the site of the high altar.

“The discovery of the bone in a pit dug into the graves in front of the high altar makes it far more likely it comes from either Alfred or Edward.”

Further tests will be carried out but the researchers are confident about the historical significance of their discovery. Dr Nick Thorpe, head of the department of archaeology, said: “The department of archaeology is extremely excited to have been able to plausibly link this human bone to one of these two crucial figures in English history.

“We also believe that we are thereby helping the city to right a historical wrong done to the remains of these great kings, which began with the dissolution of Hyde Abbey in 1539 to be followed by centuries of neglect, destruction and disturbance up to the last antiquarian diggings in 1901.

“Monks brought their remains to Hyde in 1110 because they wanted to preserve and honour them and this project enables us to do this once more.”