Nine months after they stopped being legal tender, nearly 170million of old pound coins are languishing in homes across Britain.
With people failing to return the old coins to the Royal Mint, around 169million remain stashed down the back of sofas, in pockets, drawers or small change jars.
The old £1 coins can no longer be used in shops, but they can be taken to a bank branch or the Post Office and deposited into your account.
Do you still have one? Millions of old round £1 coins are languishing in homes across Britain
Most banks can also exchange any old £1 coins for new ones.
But unlike old bank notes, old £1 coins cannot be returned to the Bank of England for their face value for an unlimited period of time after they go out of circulation.
A spokesman for the Royal Mint told BBC Wales it had expected around 85 per cent of the 1.7billion round £1 coins, or £1.4billion worth of them, to be returned during the transition period, based on the number of coins returned when the 50p coin changed in 1997-98.
‘We do not expect that all round £1 coins in circulation at the time of the transition will be returned to the Mint,’ he said.
The spokesman added: ‘Also, based on the returns of other demonetised coins we expect there to be some returns for a number of years to come as people find these.’
Have a look: It’s time to look down the back of the sofa and see what cash is lurking there
The new £1 coin was introduced into circulation in March last year, after the old version, which had been in circulation since 1983, had become ‘increasingly vulnerable’ to counterfeiting, according to the Royal Mint.
In legal tender terms, the old £1 coin was replaced with the new 12-sided version in October last year and millions of the old round ones were melted down to create the new coin.
The new £1 coin has been kitted out with a string of security features. For a start, having 12 sides make it more difficult to forge and more easily recognisable by touch.
As with the £2 coin, the new £1 is also made of two different metals, making it more difficult to replicate.
There is also small lettering used on the rim of both sides of the new coin. On one side it says ‘one pound’ all the way round and on the other it states the year of production.
All these features mean the new £1 has been labelled by the Royal Mint as the ‘most secure coin in the world.’
New version: The new £1 coin has 12-sides and is said to be the ‘most secure coin in the world’
While the new pound may be more secure than the old version, its strength in global currency markets remains variable.
The pound has fallen to a nine-month low against the euro amid fears the UK will crash out of the European Union without a trade deal in place.
Sterling is now down to €1.11 against the euro and is also down against the US dollar, the Japanese yen and the Swiss franc.
Some analysts are predicting the the pound will weaken further against the euro, which will mean British holidaymakers face increasingly more expensive holiday on the continent.