New £20 note unveiled: how much are your old banknotes worth?

The Bank of England has unveiled the design of the new polymer £20 note, featuring renowned artist JMW Turner.

Due to enter circulation in February 2020, the note will be the bank's 'most secure banknote yet'.

Read on to find out what makes it different, what to do with your old £20 notes when the new ones enter circulation, and whether you might have a rare £20 in your wallet.

Who is on the new £20 note?

Unveiled at the Turner Contemporary gallery in Margate last week, the new note features a self-portrait of JMW Turner, the 18th and 19th-century British artist known for his vivid landscape and marine paintings.

Beside him, there will be an image of the HMS Temeraire, a ship from one of Turner's most iconic works. Below Turner's signature there will be the quote 'Light is therefore colour', taken from a lecture he gave on the arts.

The note design also features an image of the Turner Contemporary gallery, and of Margate Lighthouse, which is situated nearby.

What makes the new £20 so secure?

The new £20 follows the £5 and £10 notes in shifting from paper to polymer. These plastic notes are believed to be more secure, according to the Bank of England.

Sarah John, chief cashier of the Bank of England, told Which?: 'The evidence is that counterfeiters find it much more difficult to produce counterfeits on polymer.

In other countries where they have moved to polymer notes, there have been some examples, but we have yet to see in the UK any really good attempts at counterfeiting polymer banknotes.'

Indeed, Ms John described the new £20 the 'most secure banknote yet'.

The note features foil in two different colours, with Turner Contemporary in blue, and Margate Lighthouse in gold. There's also a second polymer window in the right-hand corner, in the shape of a window from Tintern Abbey, which Turner painted in watercolour.

Ms John said: 'Those features make it much more difficult to counterfeit, even than our existing polymer notes.'

What happens to the old paper £20 notes?

The new notes will enter circulation on 20 February 2020, but you'll still be able to spend your old notes.

The Bank of England hasn't set a date yet to withdraw paper £20 notes from circulation, like it did with the paper £5 and £10 notes.

The Bank will give six months' notice before it withdraws the old notes. After that, you will no longer be able to spend them in shops.

They won't be worthless, though. Each note will hold its value, and you'll be able to take or send them to the Bank of England to exchange them for new ones.

If they're treated the same way as paper £5 and £10 notes, you'll be able to pay them into your bank account at some high street branches and at Post Offices.

As for where your old paper notes will actually end up, the Bank of England says they're either composted into a soil improver, or processed at a local energy recovery facility to generate electricity.

The £20 notes will be the third polymer notes to enter circulation, following polymer £5 notes in 2016 and polymer £10 notes in 2017.

Polymer £50 notes are expected to follow the £20 notes in 2021.

• Find out more:the Alan Turing £50 note - what you need to know

Do I have a rare £20 note?

There's one reason you might not want to exchange your old notes: collectors might be willing to buy them off you.

Most £20 notes will not fetch more than £20, but some special specimens are considered highly desirable.

While there's no guarantee your notes will ever be worth more than face value, here are the things to look out for.

Unique serial numbers

Many banknote enthusiasts are interested in serial numbers, which are found in one of the bottom corners of the note. If the number is special in some way, you might be in luck.

Sequential numbers, such as 123456 or 222222, might catch a collector's eye.

Serial numbers with multiple eights can be popular due to the number's association with luck in some Chinese communities. Another 'unique' serial code is AK47, like the famous military rifle.

High serial numbers

The higher the serial number, the later the note was printed.

If you manage to get the last paper £20 ever made, collectors might be interested in adding it to their collection.

Low serial numbers

Notes with lower serial numbers usually sell for the most money.

Since the numbers reset whenever a note's design changes, the new polymer £20 will give you another chance to find a low one.

A £5 note with the serial number A01 000004 sold for £16,800 at auction in May 2017.

It's unlikely you'll find a note this low, though, as the first notes are often given to dignitaries, such as the Queen and Prince Philip.

The note that sold for £16,800 was originally given to chancellor Anthony Barber in 1971.

Hear more about collecting rare currency with The Which Money Podcast's investigation into the dark side of rare coin investment: