People have been urged to check their change after a "botched" £1 coin turned out to be worth 600 times its face value.

62-year-old Diane Bath, who runs a Post Office in Cumbria, took delivery of coins stamped with King Charles’ face which turned out to be a goldmine.

The first coins featuring the new monarch were released back in 2022, following Queen Elizabeth II's death. All UK coins bearing the effigy of Elizabeth II will remain legal tender and in active circulation.

Diane, from the North East, spoke to the Sun after staff spotted that a £1 coin in the delivery appeared to be entirely gold.

The error by The Royal Mint meant that it was all brass, rather than the two-tone nickel.

It is believed to be an "incredibly rare" mistake and a one-of-a-kind error. “I am absolutely over the moon," Diane told the tabloid, adding: "Obviously we handle cash all of the time and it’s the most exciting find I’ve ever had in over two decades.

"I had a look online and couldn’t see one like it, so I knew it must be worth a decent amount.”

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Oliver Reece, British Coin Specialist at Baldwin’s, said: “It may not be unique but certainly they are, by their very nature, rare things and the market is quite strong for modern errors.

"I should think it would be worth a good few hundred pounds but you never know how these things will go at auction as there are often no direct comparisons.”

A Royal Mint spokeswoman said: “The Royal Mint has tight quality controls in place and the chance of encountering any UK coin with error is exceptionally low.

“We always urge collectors to be cautious and to do their research.”

Top 10 most valuable 50p coins, according to Royal Mint

  1. Kew Gardens (2009), 210,000
  2. Olympic Wrestling (2011), 1,129,500
  3. Olympic Football (2011), 1,161,500
  4. Olympic Judo (2011), 1,161,500
  5. Olympic Triathlon (2011), 1,163,500
  6. Peter Rabbit (2018), 1,400,000
  7. Flopsy Bunny (2018), 1,400,000
  8. Olympic Tennis (2011), 1,454,000
  9. Olympic Goalball (2011), 1,615,500
  10. Olympic Shooting (2011), 1,656,500

Above is a list of the top 10 most valuable coins, when they were made and how many were minted.