A RARE Roman gold coin worth up to £30,000 was initially mistaken for a sweet wrapper by a metal detecting enthusiast in south Wiltshire.

The 1,700-year-old gold one-and-a-half solidus is one of four known examples from the reign of Emperor Licinius I.

The finder, who has asked remain anonymous, unearthed the artefact after an otherwise fruitless day out with his metal detector.

He arrived late at a meeting place to find the group he was planning to join had already left, and he didn’t have a signal on his mobile phone.

“Heading home, I remembered another site which had not produced many finds for me but rather than waste the day I decided to head there,” he said.

It began to rain which made it hard to read the screen on the detector and turned the field into mud, making it difficult to walk.

“I had not had a single signal for about 15 minutes when I got a slight response - one that any detectorist will tell you is not worth digging,” he said.

“However, having had so very few signals for a while, I decided to dig it up. Six inches down I dug out a clod of earth and sticking out of the side was the unmistakeable glint of gold.

"Having dug up lots of sweet wrappers up over the years, I thought it was the foil from a packet of Rolos but on pulling it out of the mud I saw it was a coin.”

Dix Noonan Webb, the international coins and medals specialists, are expecting the coin to sell for up to £30,000 when it goes under the hammer in London on December 5.

Christopher Webb, head of the coins department at Dix Noonan Webb, said: “This is an incredibly exciting discovery which was made in the most unpromising circumstances. The three other known examples of this type are all in some of Britain’s most famous museum collections.”