British people have been urged to check their sofas and piggy banks as 145m old pound coins still have not been returned to the Royal Mint.
It is feared that many of these coins, which were discontinued in October 2017, may be lost. Just 24 million so far have been returned which is a fraction of the money outstanding.
There were about 1.7 billion round £1 coins in circulation at the start of the six-month transition period in March 2017.
The Royal Mint has reassured those who are holding on to their coins that they can still be refunded if they hand them in to their nearest bank.
Coins returned to banks and shops have been melted down to make the new £1.
A Royal Mint official said: “Our communications campaign encouraged the return of old £1 coins when legal tender was removed.
“The small proportion of coins not returned can continue to be deposited into a customer’s account at most high street banks in the UK.”
They added: “We expect there to be some returns for a number of years to come as people find these coins.”
The new coin was designed to be much more difficult to fake, with new features including a hologram image on the coin that changes from a £ symbol to the number 1 at different angles, micro-lettering on the side of the coin, being made of two metals and a “hidden high security feature” that Royal Mint has refused to reveal.