'Hundreds of millions' of the old, round pound coins have yet to be spent, as the deadline approaches for Brits to spend their change. The coins will cease to be legal tender as of midnight on Sunday (15 October).

The new pound coin design, which entered circulation in March, will replace the old at the stroke of midnight, but those who still have old coins will still be able to trade them in at banks, building societies and branches of the Post Office.

"Thanks to an agreement with all UK high street banks, everyone can deposit old pound coins into their usual high street bank account at their local Post Office branch," said Martin Kearsley, banking services director at the Post Office.

Some retailers have said they will continue to accept the coins after the deadline. Tesco will accept them until Sunday 22 October, while Iceland and Poundland will accept them for the remainder of the month.

On Saturday it was reported that there are 400 to 450 million of the older coins across the country still unspent. In the build up to tonight's deadline, people were spending the retired tender at the a rate of roughly 60 million coins a week.

"We've seen a large increase in the number of coins being brought into branch in the last couple of weeks as customers empty their piggy banks not just of round pound coins but of all their loose change," Carl Foster, head of coins at NatWest told Evening Standard.

The old one pound coin first launched in April 1983 and replaced £1 notes. More than two billion of the original coins have since been minted by the Royal Mint. The new 12-sided coin is designed to prevent the creation of counterfeits.

In recent years as many as one in every 30 pound coins has been a fake.

Since the introduction of the new coins there have been concerns that the country was not ready, in particular parking machines, many of which around the country hadn't been updated to accept them.

The British Parking Association has said it is confident that the machines are now ready for the change.