A rare £1 coin discovered by a Cumbrian postmistress has fetched twice what it was estimated to be worth at auction.

62-year-old Diane Bath, who runs The Post Office in Broughton-in-Furness, discovered the 'one-of-a-kind coin' that was accidentally created in brass rather than the usual two-tone nickel last month.

It was included in a delivery of 2023 coins straight from the Royal Mint bearing King Charles' face on September 16 and uncirculated.

READ MORE: Check your coins - Royal Mint mistakenly create King Charles £1 coins worth £600

After picking that particular bag of change to empty into the till, her colleague Siobhan later noticed it was a bit 'unusual' compared to the others.

After being unable to find a coin like it online, and not coming across such an oddity in 20 years of running the post office, Diane consulted experts who estimated the coin to be worth as high as £600.

Finally, after taking it to auction at Ryedale Auctioneers in Yorkshire on Friday, October 18, she was astounded by the amount it fetched - £1,250.

The rare £1 coin pictured as part of Ryedale's Auction (Image: Ryedale Auctioneers) She said: "Me and my husband Alan decided to make a day of it and we chose Ryedale Auctioneers because we love the TV show The Yorkshire Auction House.

"Though there was no filming taking place, we met presenter and auctioneer Angus Ashworth.

"He was really nice, very genuine and really enthusiastic about our find.

"The first bid came in at £400 then it just kept shooting up to £500 then £570.

"Finally, it was a lady on the phone who placed the winning bid for £1,250.

"Everybody clapped and it was such an exciting day.

Postmistress Diane at Broughton-in-Furness post office (Image: Broughton-in-Furness post office) "We're thrilled to bits that it's gone to someone who really wants it.

"We're sharing the money with Siobhan and Alan and I have plenty of things we're going to put ours towards.

"We have a trip to Germany soon for the Christmas markets and it's our 25th wedding anniversary and Alan's 70th birthday coming up."

Coins Valuer at Ryedale Auctioneers Jacques Tinkler added: "This was the first instance we encountered a coin with this particular error and there were no prior auction results to inform our pre-sale estimate however we anticipated strong interest from coin collectors so we assigned a valuation between £500 and £800.

"On auction day, bids came in quickly, and the coin ultimately sold to a keen coin collector in southern England for £1,250, with the buyer paying just over £1,600 including auction fees. We were very pleased to achieve such a good result for the seller."