A MASSIVE hoard of Roman coins unearthed by a Thornbury man digging a fish pond in his garden has officially became the property of the state. The 15,000-pus bronze coins - the third largest find ever in the UK - was declared treasure by a coroner and is now set to go on display at Bristol Museum.

Ken Allen, who who found the earthenware pot full of 1,700-year-old coins in March last year, will now receive a bounty when their value has been assessed by a panel of experts.

There has been speculation that the reward could go into six figures but Mr Allen is not taking anything for granted.

"In due course we shall be agreeing a figure but I'd be surprised if it was anything like the amounts that have been bandied about," said the 48-year-old father of three, a sales manager for a plastics firm. "All I can say is I'm pretty confident it will cover the cost of the fish pond which is now finished and full of fish.

"It's already more than a year since I made the find and it could be another 12 months before it's all sorted out. These things move very slowly." Mr Allen said he had contined to press museum authorities to allow at least a few of the coins to go on display in Thornbury Museum - but to no avail.

"They won't allow the collection to be split up and sadly Thornbury just doesn't have the facilities or the resources to put the collection on display," he said. "It's a great pity because I would really have liked to see the coins go on show in the town where they were found."

Bristol coroner Paul Forrest heard on Tuesday that the coins dated from between 330 and 348 AD and were struck during the reign of Emperor Constantine the Great to mark the founding of Constantinople (the present day Istanbul, the Turkey capital) as the eastern capital of the Roman Empire.

Some of the coins show a she-wolf suckling the twins Romulus and Remus - a reference to the legendary story of the foundation of Rome. The find - the most important in the region for the last 30 years - surprised archaeologists as no significant evidence of Roman occupation in Thornbury had previously been recorded.

It is believed the hoard may represent either a slow accumulation of savings, money hidden away in times of trouble, or the devaluation of coinage, when earlier coins were worth more. Mr Allen said he would never forget the Sunday morning when he stated work digging a second fish pond.

"I'd gone down about three-and-a-half feet when the spade hit something hard," he said. "I thought it was just another boulder but when I dug round it I could see it was pot of some kind, standing upright in the ground. "Then I scraped away some more clay, put my hand in and brought out a fistful of coins. I couldn't believe it, there were thousands of them." He rang Bristol Museum before transferring the coins - weighing well over half a hundredweight - into a bucket and hauling them inside the house.

Experts from the Portable Antiquities Scheme subsequenlty carried out an electronic sweep of the rest of the garden, unearthing three more coins from the immediate area but nothing further.

Commending Mr Allen for his prompt action in informing museum authorities, the coroner said: "This was an extremely good and exciting find."