After researching online he became excited when he learned similar torcs dated back to about 750BC and had fetched up to £350,000 at auction.
But tests on the piece by British Museum experts ruled it was a fake and probably less than 300 years old.
Gutted Andrew must now split the estimated £13,500 value with landowner David Hills and friends David Carr and Shaun Scott, who helped find it in July 2008.
The trio also found two gold coins from the Iron Age and a Viking ring, worth about £1,000 in total, but agreed to waive the cash after failing to reach an agreement with the landowner over ownership.
During an inquest held in Selby on Friday, British Museum curator Ben Robinson explained his conclusion the torc was fake: “It was too smooth, gold deteriorates over time, and it had too high a copper content in it.
Torc of Towton
“When I first saw a photo of it I was excited as it looked like a classic Bronze Age bracelet, but when I actually examined it I became uneasy.
“It was a very bright gold colour – usually over time gold will turn a dull mustard colour. It was too small to be a necklace but too big to be a bracelet.
“In short, it was a forgery as the dimension, colour and composition were all wrong.”
During the hearing, the three men admitted originally lying to British Museum liaison officer Amy Cooper about the exact location of the find to stop others raiding the site.
Metal detecting since the 80s, Andrew said he had found items worth a total of £20,000 in that time.
Coroner Geoff Fell ruled the items were classed as treasure, adding: “I don’t have a clue how the torc came to end up in this river. But I’m convinced it’s a forgery.”
The coins and ring will now go on display at the British Museum. The Independent Treasure Committee will decide the exact value of the fake torc and later decide its final resting place.
