A man unearthed a priceless hoard of 20,000 Roman coins as he dug a new fishpond in his back garden.
The coins are thought to date from the 4th Century
Experts say the money may date from the 4th Century and could be the biggest find of its kind in Britain.
The coins were crammed into a ceramic pot which broke up as it was dug out of the ground at Thornbury, South Gloucestershire.
Now a coroner must decide if Ken Allen, who made the discovery, can keep the treasure.
Gail Boyle, from Bristol Museum, said: "This is the most amazing find of treasure to come out of this area for 30 years."
Mr Allen said: "It was a great surprise and at first I didn't realise what we had found.
"The pot was perfectly upright; I can't believe that this discovery was only 20ft from our house."
Kurt Adams, the Finds Liaison Officer for Gloucestershire and Avon, said: "The coins identified so far can be attributed to Constantine the Great.
"The mint marks - a letter or symbol used to indicate the mint which produced the coin - suggest Trier, Germany and Constantinople as possible places of origin."
The coins are in the care of Bristol City Museum & Art Gallery where they are being cleaned in a special laboratory.
They will then be taken to the British Museum in London for further examination.
A spokeswoman for Bristol Coroner's Court said that even though the coins were found on Mr Allen's property they could still be ruled as being property of the state.
"What determines this is if the coins were buried there intentionally or lost.
"It is possible somebody put them there and forgot about them, or never intended for them to be found.
"The coroner can rule whether they are the finder's treasure or not."