A Cambridge museum has helped identify a rare coin.
Experts at the Early Medieval Corpus of Coin Finds at the Fitzwilliam Museum in Cambridge recognised the coin was 1,200-year-old silver penny, minted during the reign of Aethelberht II.
The coin, the only one of its type to be discovered, is expected to fetch between £15,000 and £20,000 at auction.
It was found by Darrin Simpson, 48, from Eastbourne, East Sussex in March.
He said: "It was a bit of a shock really, I couldn't sleep for two nights after it was identified.
"The condition is really good. This is a unique coin. I doubt if I will ever find anything better."
The coin is only the fourth ever found from the reign of Aethelberht II, a shadowy figure who ruled East Anglia in the late eighth-century.
The coin found by Mr Simpson is the first to have Aethelberht's name and the title Rex (king) on the same side.
This declaration of independence by the East Anglian king could provide a clue as to why he was murdered by a neighbouring monarch.
The coin will be auctioned in London on June 11.