The new 12-sided £1 coin enters circulation tomorrow, as the old “round pound” is set to disappear from our spare change.

The highly secure new coin has been described as the most secure coin in the world.

It means that the old “round pound” will stop being legal tender on October 15 this year.

SEE ALSO: £20,000 bill to make Watford's Pay and Display machines ready for the new £1 coin

Savers have been warned to use up their stash of old coins to make sure they are not left with currency that shops will no longer accept.

But not before they have checked their piggy bank stash to see if they have a rare £1 coin.

When will the new £1 coin come out?

It will come out on March 28 2017. From March until September will be what is known as a ‘co-circulation’ period, during which both old and new £1 coins can be accepted.

From October of 2017, businesses will stop accepting the old, round £1 coins.

If you have any left, you will be able to deposit them into your bank account – but check with your bank for details, as this may vary.

You may also be able to exchange them at the bank or Post Office if you hold an account there. But again, it’s best to check ahead of time.

When will the old £1 coins stop being legal tender?

Unlike the old £5 note which will hold its value “for all time”, the current £1 coin has a much shorter lifespan.

Experts have advised that you can take £1 coins to banks to change for notes as long as they are in bags of 20.

What does the new one pound coin look like?

The new £1 has a bold new design, which combines the English rose, Scottish thistle, Welsh leek and Northern Irish shamrock - all of which bloom from one stem within a royal coronet.

One the other side, the coin features the fifth coin portrait of the Queen.

In terms of how it feels, the new £1 coin is thinner and lighter, but slightly larger than the current coin.

St Albans & Harpenden Review:

Will there be any problems when the coin is introduced?

There are bound to be teething problems. 

The majority of supermarkets have also confirmed that their trolleys will accept the new coin from Tuesday.

Vending machines are also being adapted to accept the new coins, but it could take a while before they are all ready.

TfL has also admitted that around 5 per cent of its machines will not accept the new £1 coin on March 28.

Watford Borough Council has spent £20,000 making sure the coin will be accepted in parking machines across the town.

St Albans & Harpenden Review:

Why is the old £1 coin being changed?

Over the past 30 years, the old round coin has grown increasingly vulnerable to counterfeiters - in fact, the Royal Mint states one in 30 £1 coins is fake.

So it's time for a change. The new £1 is thinner, lighter and larger and includes a hologram-like image which alternates between '£' and '1' when seen from different angles.

There's also a secret high-security feature built into the coin itself - which will protect the coin from counterfeiting.