Medieval gold coins discovered by a metal detecting couple could go for up to £15,000 on auction.

Phil and Joan Castle found the five pieces, still in immaculate condition, in a ploughed field near their home in New Romney.

On Tuesday they will go under the hammer through specialists in London's super-wealthy Mayfair.

The couple stumbled on the find in October 2018, also discovering a broken gold coin, all from the 14th century, and a Medieval brass purse bar.

The coins are 3.4cm in diameter and are from the reign of King Edward III, showing him in a ship holding a sword and shield on one side and the royal cross on the other.

Nigel Mills, consultant in artefacts and antiquities at auctioneers Noonans, explains: “The coins were recorded as Gold nobles of Edward III, issued between 1351-61.

"This was the first significant issue of gold coins that was successful after the previous attempts had failed and those were subsequently recalled and melted down."

Mr Mills says that at the time, these were the highest denomination ones in circulation with a face value of six shillings and eightpence (33.5 decimal pence), which is about £2,500 per coin today.

He added: “Purse hoards are not common and when they do turn up they usually contain just silver coins so this one is special.

"Apart from the broken coin, which is a plated contemporary forgery, all five gold one are in virtually mint state and must have been lost.”

The purse and coins are expected to fetch £12,000 to £15,000 and will be on sale from Noonans (previously Dix Noonan Webb) who are specialist coin, medal, banknote and jewellery auctioneers.

This will be at their Mayfair saleroom in Bolton Street from 10am. The couple's find are lots 59 to 65 and are expected to be offered in the first half hour.

The Castles have been metal detecting for more than 30 years.

Mr Castle, 71, used to work at Woolwich Arsenal in London and was introduced to the hobby by his wife, who is 71. She used to search for fossils and mudlark on the River Thames.

Mudlarking is searching river mud for items of value or historical significance.

Mr Castle said: “We had no idea what the coins were when we found them. At the time, I was having chemo for leukaemia so detecting was a great relief.”

The find has been disclaimed under the Treasure Act and Mrs Castle is hoping they can have a new kitchen with their share of the proceeds, which will be split with the landowner.