A nationally significant discovery of Viking treasure dating from the 9th century was unveiled yesterday at London’s British Museum. The hoard of silver coins and jewelry found in a farmer’s field by a metal detector hobbyist has the potential to rewrite English history.

James Mather was giving up hope of getting a birthday surprise. After spending hours scanning a muddy field 40 miles west of London with his metal detector, the treasure hunter had nothing to show for his time except for some stray soda can tabs and cartridge cases, according to the Guardian newspaper. But just as the retired advertising manager was ready to find a more festive way to celebrate his 60th birthday this past October, he spotted something that resembled a silver Viking ingot he had once seen at the British Museum embedded in the ground.

James Mather, finder of the Watlington Hoard, at the find spot of discovery. (Credit: Portable Antiquities Scheme)

After digging into the mud, the amateur archaeologist discovered a mass of old coins clumped together. As the Guardian reports, Mather followed British law and phoned the government-funded Portable Antiquities Scheme, which encourages the voluntary reporting of archaeological objects found by the public, and was told to refill the hole. For several days Mather checked on the plot of farmland outside the English village of Watlington to ensure the find remained undisturbed before an officer from the Portable Antiquities Scheme could arrive and carefully excavate the block of clay holding the artifacts, which was brought to the British Museum for further examination.

A selection of items in the Watlington Hoard after examination work. (Credit: Portable Antiquities Scheme)

British Museum conservator Pippa Pearce told the Associated Press that the find looked like a “greasy clay haggis” when it arrived in her laboratory. After weeks of careful extraction and cleaning of the encased artifacts, the British Museum yesterday unveiled what they found inside the lump of soil—seven pieces of Viking jewelry, 15 silver Viking ingots and 186 rare Saxon coins. According to the Portable Antiquities Scheme, the “Watlington Hoard” dates from a turbulent time in the late 870s A.D. when the Anglo-Saxon kingdoms of Mercia and Wessex were in a fierce fight against the invading Vikings.

Although the precise circumstances of how and why the hoard was buried can never be known, archaeologists believe it likely occurred as the Vikings were forced to travel north of the River Thames to East Anglia after their decisive defeat by King Alfred the Great of Wessex at the Battle of Edington in 878 A.D. That battle marked a turning point in history that led to England’s eventual unification under the Anglo-Saxons in the 10th century.

Coin group 3 from the Watlington Hoard. (Credit: Portable Antiquities Scheme)

The silver coins—some in fragments but others well-preserved—have the potential to rewrite English history because they bear not only the images of King Alfred, but the little-known monarch of the adjoining kingdom, Ceolwulf II of Mercia, who ruled from 874 to 879 A.D. “Poor Ceolwulf gets a very bad press in Anglo-Saxon history, because the only accounts we have of his reign come from the latter part of Alfred’s reign,” Gareth Williams, the British Museum’s curator of early medieval coinage, told the Telegraph newspaper. The little recorded history of Ceolwulf, written under the orders of Alfred years after the Battle of Edington at a time when Wessex was taking control of Mercia, paints the rival king as the puppet of the Vikings. However, since the coins found in the Watlington Hoard depict the images of both Alfred and Ceolwulf, it suggests they were actually allies in the fight against the Vikings.

Only one example of the double-figured coin from each kingdom had been found previously, but the discovery shows they were more extensive than previously thought. “What we can now see emerging from his hoard is that this was a more sustained alliance with extensive coinage and lasting for some years,” Williams told the Telegraph.

“Here is a more complex political picture in the 870s which was deliberately misrepresented in the 890s after Alfred has taken over the whole of Ceolwulf’s kingdom,” Williams said. “Perhaps we should be thinking more of Stalin and Trotsky, with Ceolwulf being airbrushed out of history because he’s no longer convenient. That of course gives a very different picture of history of Alfred the great national hero, defeating the Vikings.”

LONDON, ENGLAND – DECEMBER 10: A Viking armband is held during a press preview for a rare Viking hoard discovered by metal detector enthusiast James Mather, at the British Museum on December 10, 2015 in London, England. The hoard was discovered in Watlington in Norfolk and is believed to have been buried in around 870. It was excavated as part of the Portable Antiquities Scheme and is now on display at the British Museum. (Photo by Carl Court/Getty Images)

If the hoard is legally declared to be a treasure, it will belong to the government and may be acquired by museums, with preference given to local institutions such as the Ashmolean Museum and Oxfordshire Museums Service. In addition, both the farmer who owned the field in which the hoard was discovered and Mather would receive a sizable reward—one that would make for a very welcome belated birthday present.