SCRATCHING at the earth, the young labourer immediately realised he had probably struck something valuable.

Tasked by his archaeologist boss, the two locals and a supervising foreman were excavating the former hill fort on Traprain Law in East Lothian in an attempt to unlock its mysteries. But what the men uncovered remains the largest cache of “hacked up” Roman silver ever found and and it is only now, 100 years after it was first logged, are the secrets of the Traprain Treasure finally being revealed.

Archaeologists excavating the Law found a stunning hoard of buried treasure made up of more than 250 fragments of objects that have been cut up either for exchange as bullion or for melting down and recycling into new objects.

The hoard was discovered during a routine dig ordered by Alexander Ormiston Curle, director of the National Museum, who had earlier recorded Scotland’s Ancient Monuments by bicycle.

Traprain Law had been a hill fort for centuries and Mr Curle set out to excavate it and reveal its history. He was in his office in Edinburgh on May 12, 1919, when the two local labourers made the first discovery of the silver hoard.

Immediately, one ran down to the local telephone box and called Mr Curle, but he was so paranoid about who could hear his call he did not tell him the scale of the find.

The men guarded the treasure overnight until Mr Curle arrived after lunch to see what they had found. Astonished at the scale of it, he immediately put it in boxes and called a local driver to take them to Edinburgh. Standing in East Linton waiting for the car, the men did not take their eyes off the boxes and viewed every passing local with suspicion. Eventually, they arrived at the museum and it was unpacked. There, on the tables, the hoard was revealed and it has remained on show in the National Museum ever since.

Now, after 12 years of research across Europe, Dr Fraser Hunter, principal curator of the Iron Age and Roman collections at the National Museum, has written a book about the treasure, which will be published around the centenary in May. Part of the treasure will also be temporarily housed in the local museum in Haddington. It will be the first time it has been in East Lothian since it was found.

Dr Hunter said: “The treasure is remarkable, the biggest of its kind ever found. It weighs 23 kilos (3½ stones) and tells us a lot about what was happening in the Roman Empire at the time and how important the Traprain Law hill fort was.

“Ormiston Curle’s diaries from the time paint a fascinating picture about the find and the lengths they all went to keep it secret until they got back to Edinburgh. Sadly, we only have surnames for the labourers as we wanted to get in touch with their families for the centenary”.

It is thought the hoard was buried more than 1,500 years ago, at the beginning of the Early Medieval period. Previously, it was first assumed to have been acquired by the barbarians of Traprain as “loot” stolen from retreating Romans and their allies.

But because the people at Traprain were on good terms with the Romans for several hundred years it is now believed that, rather than being about barbarians who did not appreciate the beauty of an intricately patterned dinner plate, it was more likely to have been a response to economic crisis.

At times of economic crisis people stopped trusting other forms of currency and they turned to silver and gold as it was more valuable. Now the museum has been looking at other hack silver across Europe and reinterpreting the Traprain find.

Scientists from the countries that were part of the Roman Empire have joined together in the project and it is hoped they can eventually identify where the silver was mined from using new technology.

Dr Hunter says it is also striking that many of the fragments are cut up into sizes that correlate with Roman weight standards and is “not random destruction” as it is done by people who have contact with the Roman world.

He added: “The most likely explanation is the hacking is done inside the empire and the silver is moved to Traprain Law, perhaps as a diplomatic gift, perhaps as payment for mercenary services or something like that.

“This was thought to be our barbaric ancestors descending on the soft underbelly of the Roman empire, looting and pillaging the treasure and then bringing it back here to what was called the Pirates Nest at Traprain, where it was hacked to pieces because they were barbarians.

“Suddenly, all the pretty twiddly bits no longer mattered. What mattered is the sheer weight of metal, so the bullion value becomes much more important than whether it is a fine cup or a plate or a dish.”

The Romans are known to have used bribery to try and keep their borders peaceful and secure across Europe.

After abandoning Scotland in the 160s they used bribery to keep the frontier secure and experts believe they they may have given the treasure as a bribe to prevent attacks south of Hadrian’s Wall into England, which they still occupied.

The people of Traprain Law are believed to have accepted gifts of Roman silver bullion, which they melted down and made some of the first ever items of Scottish silver jewellery. It is on show on at the National Museum of Scotland and Dr Hunter’s book will be published to coincide with the centenary, during which a series of seminars will be held. Dr Hunter added: “It’s been fascinating to work on this research and to find out things that we didn’t know before. It has shone a light on a long-forgotten world”.