A METAL detector enthusiast turned up what he thought was a washer which turned out to be a 13th-century silver-gilt brooch.

And now the piece of jewellery that Swindon pensioner Derek Alesbury found in a Wanborough field has been officially declared treasure.

Mr Alesbury, a retired electrical engineer who lives in Cullerne Road, is a member of the Wyvern Historical and Detector Society.

His find, now at the British Museum in London, was the subject of a treasure hearing before Wiltshire and Swindon assistant deputy coroner Nigel Brookes.

Mr Alesbury told how he found the brooch on December 2 after he and fellow society members received permission from the owner to search there.

He said: "It was about seven inches down and first of all it looked like a washer.

"But having got the mud and grime off, it was obvious there was engraving and a place where a pin would have been attached.

Mr Alesbury took it to Winchester Museum, from where it was sent to the British Museum, and a report was prepared by James Robinson, curator of Medieval Antiquities.

Mr Robinson wrote: "The brooch dates from the 13th century and examination has established the metal to be silver gilt the brooch is made of silver and has been gilded."

Mr Brookes said one of the official definitions of treasure, which must be handed to the Crown in exchange for its market value, was a metal object other than a coin with a precious metal content of more than 10 percent.

After the hearing, Mr Alesbury revealed that he has yet to be advised of the value of the brooch.

He also revealed that he has been using a metal detector for only two years, and that the brooch was his most important find to date.

He has previously unearthed various coins, dating from Roman times to the Victorian era.

The landowner asked not to be named for fear of attracting unauthorised treasure hunters to his property.