After centuries underground, the dirt-encrusted object gave little hint of what it would reveal.
But painstaking conservation work has revealed what experts are now hailing as “the most important British Celtic art object of the millennium”.
The remarkably well preserved bronze shield, with a swirling pattern design, formed part of a unique chariot burial, which also contained the upright skeletons of two ponies found on a building site at Pocklington in 2018.
Its owner, a highly regarded member of his community, was in his late 40s or older when he died, between 320BC to 174BC.
He was given a spectacular send-off, with his body placed in the chariot behind the horses, placed to look as if they were leaping out of the grave.
The type of burial has no parallels in the UK. Intriguingly, a similar-looking chariot burial with horse skeletons,dating to the third or fourth century BC was discovered in 2013 in Svestari in north-east Bulgaria.
Archaeologist Paula Ware from MAP Archaeological Practice said she was amazed by the results of specialist conservation, which shows the shield was decorated in the La Tène style, typical of early Celtic art.
The asymmetrical design, with triple spiral motifs, was made by hammering the bronze sheet from underneath and draws attention to the central raised boss. It also has a scalloped border, a previously unknown design feature, not comparable to any other Iron Age find across Europe.
Leather and wood fittings on the back of the 75cm shield have rotted away.
Miss Ware said the burial - found at Persimmon Homes’s The Mile development - indicated a belief in an after life. She said: “These horses were placed with their hooves on the ground and their rear legs looking as though they would leap put of the grave.
“For me that definitely indicates that they were moving onto something else - he has his food, weapons and the means of travel.”
Whether the horses went alive or dead into the grave is not known - no signs of a ramp have been found.
The shield was well used and a slash made by a sword is clearly visible in the upper right hand side. The only other shield quite like it, the famous Wandsworth shield boss, which was found in the Thames river in 1849, is now in the British Museum.
“We don’t know how the man died,” said Miss Ware. “There are some blunt force traumas but they wouldn’t have killed him. I don’t think he died in battle; it is highly likely he died in old age.
“What his role was I can’t tell you. He has collected some nice goodies along the way - he is definitely not run of the mill.”
His head was surrounded by the bones of six piglets, believed to be an offering, and a decorative bronze and red glass “dragonfly” brooch was also left with him.
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She said: “The popular belief is that elaborate metal-faced shields were purely ceremonial, reflecting status, but not used in battle.
“Our investigation challenges this with the evidence of a puncture wound in the shield typical of a sword.
“Signs of repairs can also be seen, suggesting the shield was not only old but likely to have been well-used.”
It was found 60m from the grave of a younger injured male, aged 17 to 25, who had been “ritually speared” with 10 iron and bone spears. Bits of a broken shield was also found with that grave.
The hope is the stunning Iron Age artefacts will eventually go into a new museum at nearby Burnby Hall.
Scott Waters, the director in charge at Persimmon Homes Yorkshire, said: “The excavation at The Mile development is a truly magnificent discovery for British history and we feel this recognition and find should remain in the local area.”
The full academic report is expected to be published in the spring. However, it is such a significant find that it is likely that research will take years, and the story of the warrior and his chariot will keep on evolving.
The excavation is now complete and many new residents have already moved into their new homes.