This time tomorrow Andy Carter could be £250,000 richer.

In October 2019, the Norwich metal detectorist found a rare 'leopard' gold coin, dating back to the reign of Edward III, in a field near Reepham in north Norfolk.

His discovery is finally up for auction on Tuesday (March 8).

Mr Carter, a 65-year-old retired research scientist, discovered the coin at a charity day, known as a rally, involving about 30 detectorists.

"That particular day hadn't been that productive," he said. "By 3.30 in the afternoon I was one of only three people left in the field. The others were all packing up, getting ready to go."

He was walking in the opposite direction when his metal detector picked up a faint signal.

"I dug down, it was deeper than I'd expected, ten inches down," he said.

"It was just lying at the bottom of the hole. It was folded over gold coin, an inch in diameter.

"I thought, 'I can't believe it'."

Mr Carter picked up the coin, brushed off some of the muck, and spotted the leg of a wild cat, either a lion or a leopard.

He initially thought leopard.

When he had first started detecting, 30 years before, he read a book which described an extremely rare gold 'leopard' coin from the reign of Edward III in the 14th century.

"Before going out detecting I used to joke, 'I'm going out to find a leopard.' So I thought this can't be a leopard, they're as rare as hen's teeth."

But when he brushed off some more muck he saw the letters 'EDW'.

"Then I knew what it was. To find any gold coin is a miracle. But this was very rare and very valuable."

So rare, in fact, it was only the sixth gold 'leopard' coin ever found - and one of those was almost unrecognisable.

Mr Carter started metal detecting in 1998 and since retiring four years ago has been going out most weekdays.

He said: "It's really a random search. 99pc of the time what you find is scrap metal. I normally spend £5 in diesel and come back with about 50p worth of scrap metal. It's not a hobby to earn money from.

"It's really for the love of history," he adds. "To dig up a coin or a brooch and know you're the first person to touch it for hundreds or for thousands of years, it's quite an addictive feeling, it's a buzz."

In 2001, he unearthed a Bronze Age hoard which had lain undisturbed for almost 3,000 years. There were axe heads, spear heads, woodworking tools, knives, and fragments of sword blade.

"All the history that's passed by while these things have been silently waiting in the ground, and then you come upon them," he said.

The auction begins at 10am on Tuesday (March 8) at Dix Noonan Web in London.

Mr Carter said: "Because of the pandemic, the price of gold bullion and hammered gold coins has gone through the roof."

The starting price for the coin is £100,000 but it could go for up to £500,000. The money will be split evenly by Mr Carter and the owner of the land where he found the coin.

"It's a life-changing amount of money," Mr Carter said. "I told my fiancee the coin could be worth more than our house."

With the windfall, depending on how much the coin is sold for, the couple will buy either a new kitchen or a new house altogether.

In the meantime, Mr Carter continues to travel the county and trudge across muddy fields with his metal detector, waiting to hear the signal.

"It's an addiction really. Once you've found something old, it keeps you going," he said.

History of the gold 'leopard'

The leopard florin was minted in 23 carat gold at the Tower of London in January 1344.

It features a leopard sitting upright wearing a banner and had a face value of three shillings or 36 silver pennies - worth approximately a month's salary for the average person at the time. Its value was £1,000 to £2,000 of today's money.

The coin was exclusively used by rich merchants and aristocrats for paying fines and buying and selling houses.

But it was withdrawn after only six months because gold was worth more in bullion than in the coin itself.

Edward III issued a royal proclamation to demonetize the coins and they were handed in to be melted down.

Except for Mr Carter's discovery, only five other such coins are known to still exist. Three were sold at auction before 1960 with two now in the British Museum and the third is at the Ashmolean Museum in Oxford.

Treasure goldmine

Norfolk has an impressive record for buried treasure.

Coins are the most commonly found object, followed by buckles, pots and brooches.

Archaeologist and UEA graduate Tom Lucking hit the headlines in 2014 when he found a seventh century haul of Anglo-Saxon gold in a grave buried at a field in Winfarthing.

Mel Hollowger discovered a seventh century pyramidal mount and a gold strip in a location in north Norfolk two days before Christmas in December 2018.

And in November last year, it was announced that a metal detectorist near King’s Lynn had unearthed the largest Anglo-Saxon treasure hoard ever discovered.

Detectorists can take finds home provided that they obtain export licences for items more than 50 years old.

But if a find qualifies as treasure under the Treasure Act it may be compulsorily purchased by a museum.

The proceeds are then split between the finder and landowner.