People urged to check their pockets after two 50p Brexit coins minted with the wrong exit date are discovered

Around a million of the special coins to mark the planned Brexit day of 31 October 2019 were melted down and recycled after then prime minister Boris Johnson

People are being urged to check their pockets after two 50p Brexit coins minted with the wrong exit date were discovered.

Around a million of the special coins to mark the planned Brexit day of 31 October 2019 were melted down and recycled after then prime minister Boris Johnson was forced to seek an extension by Parliament.

It was believed all of them were destroyed - but two surviving coins have now surfaced, and are said to be worth tens of thousands of pounds.

Gregory Edmund, a numismatic specialist from Spink & Son auction house, told The Telegraph: “Ever since the official London Gazette notice for the 2019 Brexit 50 pence has existed, I have wondered if survivors of the one million cancelled coins would one day surface.

“Given the extremely stringent security at the Royal Mint, to suddenly have two examples survive, and be available for study at the same time, is a unique opportunity.

“This truly feels like my Charlie Bucket moment discovering the numismatic Golden Ticket.”

A thousand trial coins had also been made to mark the first exit date of March 29 2019, which was missed by Mr Johnson’s predecessor Theresa May.

The coins were recycled into new “gold, silver and cupro-nickel coins” featuring the updated exit deadline of 31 January 2020.

The two October deadline coins were handed to Spink & Son and are the only two coins known to be in circulation - although a Royal Mint spokesman said they were unable to confirm the validity of the coins.

Mr Edmund told The Telegraph that if the coins went up for auction he would expect them to fetch more than £40,000.

He has set up a hotline for people who have found another one of the rare coins to come forward.

At the time they were put into circulation, the Brexit coins sparked controversy before entering circulation – and not just for political reasons.

Their inscription reads: “Peace, prosperity and friendship with all nations.”

Author Sir Philip Pullman called for the coins to be boycotted for not having an Oxford comma and wrote on Twitter that the omission meant the coin should “be boycotted by all literate people”.

An Oxford comma is used after the penultimate item in a list of three or more items, so would be placed after the word “prosperity”.